# recovery of gold from ores with chlorine in 1898



## Traveller11

From "Getting Gold: A practical treatise for prospectors, miners and students" Written by J.C.F. Johnson, F.G.S. (1898)


The most scientific and perfect mode of gold extraction (when the conditions are favourable) is lixiviation by means of chlorine, potassium cyanide, or other aurous solvent, for by this means as much as 98 per cent of the gold contained in suitable ores can be converted into its mineral salt, and being dissolved in water, re-deposited in metallic form for smelting; but lode stuff containing much lime would not be suitable for chlorination, or the presence of a considerable proportion of such a metal as copper, particularly in metallic form, would be fatal to success, while cyanide of potassium will also attack metals other than gold, and hence discount the effect of this solvent.

The earlier practical applications of chlorine to gold extraction were known as Mears' and Plattner's processes, and consisted in placing the material to be operated on in vats with water, and introducing chlorine gas at the bottom, the mixture being allowed to stand for a number of hours, the minimum about twelve, the maximum forty-eight. The chlorinated water was then drawn off containing the gold in solution which was deposited as a brown powder by the addition of sulphate of iron.

Great improvements on this slow and imperfect method have been made of late years, among the earlier of which was that of Messrs. Newbery and Vautin. They placed the pulp with water in a gaslight revolving cylinder, into which the chlorine was introduced, and atmospheric air to a pressure of 60 lb. to the square inch was pumped in. The cylinder with its contents was revolved for two hours, then the charge was withdrawn and drained nearly dry by suction, the resultant liquid being slowly filtered through broken charcoal on which the chloride crystals were deposited, in appearance much like the bromo-chlorides of silver ore seen on some of the black manganic oxides of the Barrier silver mines. The charcoal, with its adhering chlorides, was conveyed to the smelting-house and the gold smelted into bars of extremely pure metal. Messrs. Newbery and Vautin claimed for their process decreased time for the operation with increased efficiency.

At Mount Morgan, when I visited that celebrated mine, they were using what might be termed a composite adaptation process. Their chlorination works, the largest in the world, were putting through 1500 tons per week. The ore as it came from the mine was fed automatically into Krom roller mills, and after being crushed and sifted to regulation gauge was delivered into trucks and conveyed to the roasting furnaces, and thence to cooling floors, from which it was conveyed to the chlorinating shed. Here were long rows of revolving barrels, on the Newbery-Vautin principle, but with this marked difference, that the pressure in the barrel was obtained from an excess of the gas itself, generated from a charge of chloride of lime and sulphuric acid. On leaving the barrels the pulp ran into settling vats, somewhat on the Plattner plan, and the clear liquid having been drained off was passed through a charcoal filter, as adopted by Newbery and Vautin. The manager, Mr. Wesley Hall, stated that he estimated cost per ton was not more than 30s., and he expected shortly to reduce that when he began making his own sulphuric acid. As he was obtaining over 4 oz. to the ton the process was paying very well, but it will be seen that the price would be prohibitive for poor ores unless they could be concentrated before calcination.

The Pollok process is a newer, and stated to be a cheaper mode of lixiviation by chlorine. It is the invention of Mr. J. H. Pollok, of Glasgow University, and a strong Company was formed to work it. With him the gas is produced by the admixture of bisulphate of sodium (instead of sulphuric acid, which is a very costly chemical to transport) and chloride of lime. Water is then pumped into a strong receptacle containing the material for treatment and powerful hydraulic pressure is applied. The effect is stated to be the rapid change of the metal into its salt, which is dissolved in the water and afterwards treated with sulphate of iron, and so made to resume its metallic form.

It appears, however, to me that there is no essential difference in the pressure brought to bear for the quickening of the process. In each case it is an air cushion, induced in the one process by the pumping in of air to a cylinder partly filled with water, and in the other by pumping in water to a cylinder partly filled with air.
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I'm a bit short of time right now but tomorrow or the next day I would like to explore how the HCl/Clorox process evolved from this method. I also believe that a very basic mistake was made and that the HCl/Clorox method has far more potential for dealing with black sand concentrates than has been believed up to this point. Read this article very carefully and check back in a couple of days. There are several very important clues in this article.


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## Traveller11

I would like to begin a discussion of the various ways of leaching gold with chlorine and the similarities between them. I would first like to re-post the post that first started me wondering about the possibility of using a chlorine leach with an iron rich ore. Here, once again, from james122964, and hats off to this rebel and independent thinker:

From james122964:

I would try the HCL/chlorox leach first, but use a sealed container, cut way down on the HCL, and use enough chlorox to convert nearly all of the HCL to chorine gas. 
DO not use a glass container, use a 5gl bucket with lid.

I use this for IC chips. I put the ground chips in to about 1/3 of the bucket deep, then I use HCL which the amount depends on the expected metal content, to much does not hurt but is wastefull, I put this in a plastic drink cup (disposable) and force it down into the ground material (so it does not spill) I then add the chlorox which is also in a plastic cup and force down so it will not spill.

I drill a 1/2 inch hole in the lid (relief valve, kinda thing) that I have a rubber stopper to fit. snap the lid on tight. Now here is the tricky part, tip the bucket so the HCL and chlorox mix, then set the bucket back level and test for chlorine gas coming out of the hole with a q-tip that has been dipped in ammonia, white fumes will tell that the bucket is full of chlorine, once this happens cork the hole and roll the bucket around to mix the chlorine gas with the "ore" leave this set for at least 24 hours, rolling again to mix about every six hours or so.

When this is done you can extract the gold by rinsing with water and draining, I reuse the water several times to get a high enough concentration to drop the gold from.
You can then extract your silver chloride with the thiosulfate, I do not bother because of the low value of silver and low content in my IC powder. If your ore has higher then it may be worth it.

The HCL is what reacts with the iron oxides, by eliminating the excess HCL and using chlorine gas, hardly any of the iron compounds are reacted with.

I think if you get the process above down, then you will not really want to use the thio, as you skip many steps involved in the thio process.

This is my adaptation of the Plattners Process that has been used for 100 or so years.

Jim
~~end quote~~

What surprised me the most is that when james posted this, it was completely ignored (except for myself). And yet, if his reports are accurate, he seems to have solved the age old problem of separating ultra fine gold from ores rich in iron oxides, using nothing but solutions available at any hardware store.

The gist of what james is saying seems to boil down to using way less HCl than usual in the HCl/NaOCl process, ultimately leading to a leach with a much higher, though still acidic, ph. I have read many times on this forum that it requires a very low ph to put iron oxides into solution. I wonder if this is what prompted james to try using less HCl in his process?

Let's take a look at what actually happens when HCl is added to NaOCl bleach.

NaOCl bleach (6%) is a mixture of 94% water and 6% NaOCl. It is often produced by the electrolysis of NaCl and water but it can also be produced by mixing hypochlorous acid (HOCl) and sodium hydroxide (NaOH). HOCl + NaOH = NaOCl + H2O. When NaOCl is produced by the electrolysis method, NaOH is added to it until the ph of the NaOCl bleach is raised over 12. This stops NaOCl from becoming HOCl.

So, what happens in the HCl/NaOCl leach when HCl is added to NaOCl? First, the ph drops below the critical 11.86 point and hypochlorous acid (HOCl) and sodium hydroxide (NaOH) are formed. NaOH and HCl react to form NaCl + H2O, neutralizing each other. More HCl is added, negating more NaOH until an acidic solution of HOCl and H2O is achieved. The question is, just how low does the ph have to go to put gold into solution? And an even better question is, do we have to keep lowering the ph until Cl2 gas is formed or can we use the acidic solution of HOCl and H2O at a higher ph, to dissolve gold, without making Cl2 gas?

This is what makes james' process of using so much less HCl so interesting. By doing so, he obviously does not achieve a ph of 1 or 2 but is likely more in the range of 5-6. Looking at the Plattner's Process in my first post, I believe these fellows in 1898 were achieving exactly the same objective, just starting out with different compounds. By introducing Cl2 gas, under pressure, to a mixture of water and ore, they caused the Cl2 to be dissolved in water that began with a neutral ph of 7. Once dissolved, Cl2 combines with water to make HOCl and HCl. As the water was ph 7 to begin with, and a limited amount of these two acids would be formed by adding Cl2 to water, would the final ph of the leach solution not be identical to the james122964 variation of the HCl/NaOCl leach solution, likely in the range of 5-6? Have they not made exactly the same thing at almost the same ph?

I know this post is getting a bit long but, carefully read this material below from the 1890's and tell me if the sodium hypochlorite solution (ultimately becoming hypochlorous acid) produced by this electrolytic method does not ultimately become the same solution as james122964's variation of HCl/NaOCl or the original Plattner's Process in my first post. Remember, NaOCl produced electrolytically does not have the 12+ ph of NaOCl sold as bleach (no NaOH added to it) and does not require copious amounts of HCl to bring its ph under 7.

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Electrolytic Precipitation of Gold








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In order to perform the electrolytic precipitation of gold, from the filtration vessel the gold chloride solution was conducted into the outer or battery jar of an electrolytic cell. The electrode of the outer cell was connected with the negative pole of a dynamo and the electrode on the inner cell was connected with positive pole or terminal of the dynamo. The gold solution was sent into the jar near the bottom and slowly circulated upwards, and at the same time a current of electricity was passes through the cell. When the reaction was produced, the gold chloride was decomposed and felt like a shower of fine spangles to the bottom, while the liberated chlorine passed into the inner cell where it was absorbed by the water circulating and formed a chlorine solution.

The receiver was charged with chlorine solution generated by the electrolysis of salt. The unit comprised a battery, a conductor from the electrode in the large battery jar to the negative pole of the electrical generator, the conductor from the electrode in the porous cell to the positive pole of the generator, a reservoir containing a saturated solution of sodium chloride, which passed to the battery through a pipe and a reservoir containing water connected by a pipe with a porous cell.

In order to treat the ore more effectually with the chlorine solution it was advantageous to expel the air from the chlorinator. For this purpose the chlorinator was provided with a valve, so that the air contained in the chlorinator passed out as the chlorine solution passed in. the valve was closed immediately the air was expelled. The chlorinator after disconnected was slowly revolved by means of a pulley and strap from an engine, or in other suitable way until the gold was dissolved as a gold chloride. The time required for treatment in the chlorinator varied from one to two hours according to the characteristics of the gold ore treated. The ore and solution were discharged into a suitable filtration vessel placed beneath the chlorinator. The vessel was a shallow vat constructed of oak or other material, the lower part was made cone-shaped and of the same capacity of the chlorinator.

The vat was closed by a cover bolted down. In the center of the cover there was hopper-shaped inlet for receiving the ore and solution from the chlorinator. A perforated diaphragm covered with asbestos cloth, over which was advantageously placed a layer of other suitable filtration media such as ground asbestos, which was fixed from one to two inches below the top of the vat. The gold chloride was washed out of the ore by a stream of water from a tank. The water entered the vat through a pipe at the lowest part and percolated upwards through the ore until the gold content in the solution was extremely low. It was important to take samples of the solution to determine the presence of gold. A sliding door in the bottom of the vat was opened and the residue from the ore as discharged by means of a large outlet opened into a truck placed underneath.

The gold chloride and water descended through a pipe into a receiver and was conducted from the receiver into the outer or battery jar of the electrolytic cell. The gold solution flowed into and entered the jar at the bottom and slowly circulated upwards and at the same time a current of electricity was passé through the cell to reduce and precipitate gold from the solution into a perfectly pure state, upon the bottom of the jar, from where it was removed. The chlorine was liberated at the same time at the electrode in the inner or porous cell and in contact with the water circulating and formed a chlorine solution, which was sent to receiver vessel.


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## butcher

Roasting the ore would be a very important step, no only to drive off sulfates but also to help form acid resistant iron hydroxide, to help keep from leaching iron as much as possible in the acidic leach (as you described in your other post).

Hypochlorite is basic (with NaOH keeping the chlorine in the water) to generate chlorine gas we need to make it acidic (if electrolysis is not involved), if electrolysis is involved we can generate chlorine by splitting a chloride salt, the sodium Na+ to the cathode, the chlorite CLO- to the anode to generate chlorine, water in the solution will also split to hydrogen H+ and hydroxides OH- hydrogen gas would gas off of cathode.

In electrolysis salts of chlorides the anode can form chlorine, the cathode can form hydroxides (one reason for the split cell salt bridge, or asbestos sheet membrane separating these two compartments of the cell to assist to keep these from mixing back together) to keep the negative hydroxides from moving to the anode and also to help to keep a rich sodium chloride solution around the anode to generate chlorine gas from.


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## Traveller11

butcher said:


> Roasting the ore would be a very important step, no only to drive off sulfates but also to help form acid resistant iron hydroxide, to help keep from leaching iron as much as possible in the acidic leach (as you described in your other post).
> 
> Hypochlorite is basic (with NaOH keeping the chlorine in the water) to generate chlorine gas we need to make it acidic (if electrolysis is not involved), if electrolysis is involved we can generate chlorine by splitting a chloride salt, the sodium Na+ to the cathode, the chlorite CLO- to the anode to generate chlorine, water in the solution will also split to hydrogen H+ and hydroxides OH- hydrogen gas would gas off of cathode.
> 
> In electrolysis salts of chlorides the anode can form chlorine, the cathode can form hydroxides (one reason for the split cell salt bridge, or asbestos sheet membrane separating these two compartments of the cell to assist to keep these from mixing back together) to keep the negative hydroxides from moving to the anode and also to help to keep a rich sodium chloride solution around the anode to generate chlorine gas from.



I fail to understand why you are so stuck on the idea of making chlorine gas.


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## butcher

I do not know I guess to get the gold to form a gold chloride.

I was under the assumption that was the purpose to get the gold in an state of oxidation through electrolysis (or with chlorine in the case of HCl/NaCLO with chlorine dissolved in solution) and then get the gold to form a gold chloride from the attaching the ion to the free chloride ions in solution.

Without oxidizing the gold how would you get the gold to form chlorides, chlorides alone will not oxidize elemental gold, the chloride have all of their electrons and will not take an electron from the gold atom, unless we can remove an atom from the gold first it will not form gold chloride (this is why gold will not dissolve in HCl alone, the acid is not a strong enough oxidizer, but when we add chlorine gas dissolved in solution the chlorine in its elemental form is missing electrons, it will easily take an electron form the gold, the chlorine now with a full shell of electrons now forms a salt of chloride ion, this gold ion with the missing electron can now be joined to three chloride ions to form a solution of gold chloride.

You will need to oxidize the gold before it can join with chloride ions, how would you oxidize the gold without an oxidizer like chlorine or nitric acid?
In a salt cell we generate chlorine at the anode when we split the salt, and the salt also supply's a ready supply of chloride ions for the gold to attach to.

I guess I am missing something here with where you are going with this idea, but at this point I do not understand what it is.

Maybe I am just missing the point completely?


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## Traveller11

butcher said:


> I do not know I guess to get the gold to form a gold chloride.
> I was under the assumption that was the purpose to get the gold in an state of oxidation through electrolysis (or chlorine in the case of HCl/NaCLO with chlorine in solution) and then get the gold to form a gold chloride from the attaching chloride ions in solution.
> 
> Maybe I am missing the point?



I believe the words "chlorine in solution" pretty much sum up what I am trying to say. In the thread "Salt Water Electrolytic Cell", I quoted a description, from the 1890's, of an electrolytic cell that created, from salt water, a chlorine solution that would, in a separate chlorinator, put gold into solution as a chloride. The same cell would also dissociate this gold chloride into gold and chlorine gas. BUT, the recycled chlorine gas existed only briefly at the anode before it became a chlorine solution and was returned to the chlorinator to dissolve more gold.

The electrolytic cell described in the article can only be one thing; a sodium hypochlorite generator. It may also have produced sodium chlorate in solution, depending on the temperature the cell ran at, but I believe the main product was sodium hypochlorite. We know it was not making chlorine gas because nowhere in the article does it mention a membrane separating the anode and the cathode. Also, from the cell, it says a chlorine solution, and not chlorine gas, is sent to the chlorinator to dissolve gold. There is also no mention of HCl being added to the NaOCl to allow the release of Cl2 gas. We can only assume this solution had a ph of 5-6, created when sodium hypochlorite in water at a ph of less than 11.86 becomes hypochlorous acid.

In other words, the chlorine solution from this cell was able to put gold into solution without making one wisp of Cl2 gas.


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## butcher

OK from the sounds of it, we can still be talking the same language,

I did not necessarily mean the chlorine had to leave solution as a gas,
But the chlorine will still be generated at the anode from the solution, the chloride is reduced at the anode to chlorine, Gas whether it leaves as gas or reacts with gold or other salts acids or bases in solution and stays in solution as another form, the electrical current is taking electrons from the chloride to make elemental chlorine at the anode. the chlorine can now take electrons from the gold so the gold can be bound to three free chlorides in solution. or the chlorine could mix with water in a basic solution and make chlorides or chlorates, or if solution was acidic leave as a gas, Much of whether the chlorine generated at the anode will leave the cell as gas or stay in the cell to react, can be several factors, temperature, pH, dilution, reaction with other metals (acids or hydroxides or other salts in the cell), current and voltage and so on.


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## Traveller11

butcher said:


> OK from the sounds of it, we can still be talking the same language,
> 
> I did not necessarily mean the chlorine had to leave solution as a gas,
> But the chlorine will still be generated at the anode from the solution, the chloride is reduced at the anode to chlorine, Gas whether it leaves as gas or reacts with gold or other salts acids or bases in solution and stays in solution as another form, the electrical current is taking electrons from the chloride to make elemental chlorine at the anode. the chlorine can now take electrons from the gold so the gold can be bound to three free chlorides in solution. or the chlorine could mix with water in a basic solution and make chlorides or chlorates, or if solution was acidic leave as a gas, Much of whether the chlorine generated at the anode will leave the cell as gas or stay in the cell to react, can be several factors, temperature, pH, dilution, reaction with other metals (acids or hydroxides or other salts in the cell), current and voltage and so on.



Precisely. But, if the ph of the water is close to 7 before the NaCl is added to it, electrolyzing the brine should give you a mildly acidic solution of water and hypochlorous acid. Adding a limited amount of HCl to a basic solution of NaOCl in water should give us the same thing. I believe this is what james122964 tumbled to about the HCl/Clorox method; the fact that far too much HCl was being added, reducing the ph to 1-2, and iron and its oxides were being dissolved along with the gold (as well as copious amounts of CL2 gas being given off).

I'm waiting for a ph meter to arrive from an Ebay site I ordered it from. I have a great deal of black sand gathered from a place assayed many times over and found to have goodly amounts of microscopic gold. I plan to prepare a leach solution from Clorox by slowly adding minute amounts of HCl to it until the ph is just below 7. I will prepare similar solutions at 6.5, 6, 5.5, 5 and 4.5. Each will be applied to an equal amount of black sand concentrate, filtered and the resulting solution tested with SnCl.


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## butcher

we could start an electrolytic with neutral pH salt, but as we ran the cell the pH could change drastically during operation.

H+ + OH- --> H2O water is neutral pH at the cathode in the electrolytic cell the H+ will move to the cathode, The OH- will move to the anode, the H+ is reduced at the cathode as hydrogen gas leaving the cell as H2 gas, now the pH of the cell becomes basic.

I Know now I am so stuck on hydrogen gas :lol:


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## Traveller11

butcher said:


> we could start an electrolytic with neutral pH salt, but as we ran the cell the pH could change drastically during operation.
> 
> H+ + OH- --> H2O water is neutral pH at the cathode in the electrolytic cell the H+ will move to the cathode, The OH- will move to the anode, the H+ is reduced at the cathode as hydrogen gas leaving the cell as H2 gas, now the pH of the cell becomes basic.
> 
> I Know now I am so stuck on hydrogen gas :lol:




LOL :lol: Well, you do bring up a good point. Not one of these 100+ year old articles I've been reading ever once state, "...and when the chlorine solution came out of the electrolytic cell, on its way to the chlorinator, it had a ph of (__) ..." or "......and when the chlorine gas was forced into the chlorinator at 60 psi and dissolved in the water contained there, the resulting ph of the chlorine solution was (__)...". Even james122964, with his variation of the HCl/Clorox process that used a greatly reduced volume of HCl, does not tell us what the resulting ph of his solution is.

This leads me to ask, does a chlorine leach actually have to be acidic to be able to put gold into solution as auric chloride? Any idea what the best ph would be to dissolve gold and avoid dissolving iron oxides?


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## Platdigger

No, I have heard of it being done on the alkaline side (with chlorine) as well.


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## Traveller11

Platdigger said:


> No, I have heard of it being done on the alkaline side (with chlorine) as well.



Thanks for that, Platdigger. I guess this means I'll have to expand my experiment to include basic solutions of chlorine, as well.


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## Gratilla

james122964, I believe, is the same James that has been sharing his chlorine method for some years over on MicronGold Yahoo Group. Also, Art, the late founder of the group, did quite a bit of work on a salt cell some years ago. A search of the message and file archives should turn up some interesting hits.

BTW, has anyone considered corresponding directly with the SALTEM patent holders? As a semi-govt org committed to stamping out artisinal mercury use, I doubt they would be secretive about their system. I would be interested in details of any up-and-running systems. If they require parties nearby artisinal mercury users in order to correspond, I'll volunteer (in return for an email address) - lots of kampung Hg users in these parts.


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## Traveller11

Gratilla said:


> james122964, I believe, is the same James that has been sharing his chlorine method for some years over on MicronGold Yahoo Group. Also, Art, the late founder of the group, did quite a bit of work on a salt cell some years ago. A search of the message and file archives should turn up some interesting hits.
> 
> BTW, has anyone considered corresponding directly with the SALTEM patent holders? As a semi-govt org committed to stamping out artisinal mercury use, I doubt they would be secretive about their system. I would be interested in details of any up-and-running systems. If they require parties nearby artisinal mercury users in order to correspond, I'll volunteer (in return for an email address) - lots of kampung Hg users in these parts.



I have made an effort to contact people within SALTEM to find out more information about this process. It does not seem to be something that is being actively pursued by them at this time. No one there is able to provide me with anything more than the sketchiest details.

All things considered, the SALTEM electrolytic process is so simple, I think the easiest thing to do is just go out and build a cell. It seems graphite or titanium electrodes would be most suitable.

I just wish it had been stated whether the cell was making sodium hypochlorite or sodium chlorate. The same cell can make either compound, depending on the current applied and the resulting cell temperature. Below, 50° C., sodium hypochlorite is produced. Between 50-70° C., sodium chlorate is produced. I was a bit concerned that, once sodium chlorate (NaClO-3) was made, that the cell could then go on to make sodium perchlorate (NaClO-4, and ultimately perchloric acid - a very dangerous substance to have around) but I found, through further study, that making perchlorate in a cell is a fairly complicated thing to do and not something that would happen by accident.


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## NoIdea

Anyone see this, might point to something a little different, too many assumptions though for my liking. 8

http://labmem.unsl.edu.ar/Publicados/Ojeda_09.pdf

Deano


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## Traveller11

Platdigger said:


> No, I have heard of it being done on the alkaline side (with chlorine) as well.



Here is confirmation of what you have heard. I found this on the Prospector's Paradise. Unfortunately, the guy who wrote it passed away a while ago. I would have loved to discuss this with him.

"Remember chlorine is very slow. You will have to maintain this system for several hours to a day or more. 

Like all of the halides, if you allow the solution to go acid, the chlorine will rapidly boil off and if you are close by will be extremely uncomfortable. Bromine and iodine are not so bad. They are not nearly so volatile and will give you a little more time to rectify the situation by addition of a little lye water. 

If you are extracting with halides, in particular, chlorine where you have no visual reference as to what is happening, you should have some hydrochloric (muriatic) or sulfuric acid at hand. If your reaction should start to slow down and you are sure you have an excess of halide in solution you might have to add a little acid in order to liberate the halide from it’s salt form in order to keep sufficient free halide to ensure a good extraction. If you can keep the pH at say 8.5 you will be about right.

If chlorine production should get out of hand, you probably should have some solution of sodium thiosulfate on hand. It can be bought from any chemical supply. This is the stuff that tropical fish freaks use to treat tap water to destroy chlorine. You will need much more than they use however. This is a good way to neutralize any solution you wish to dump. Your neighbors will probably appreciate your thoughtfulness."


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## Barren Realms 007

Would the use of slow dissolving chlorine tablets keep a supply of chlorine in the solution and just keep a check on the PH?


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## Traveller11

Barren Realms 007 said:


> Would the use of slow dissolving chlorine tablets keep a supply of chlorine in the solution and just keep a check on the PH?



The idea never occurred to me but, thinking it over, it might be an incredibly effective way of mimicking the original Pattner's & Mears' Process in which chlorine gas was bubbled up through a mixture of ground ore and water and, once enough Cl2 was in solution, the vessel was turned for several hours to leach the gold out of the ore. They found, of course, that the Cl2 gas went into solution quicker if the vessel was pressurized with air to 60 psi. The Cl2 put into solution combined with the water to make hydrochloric and hypochlorous acid (HCl + HOCl). 

I've never encountered slow dissolving chlorine tablets before. Do you know the chemical compound for them? Do they release Cl2 gas or Cl2 in solution? I'm wondering if they are not calcium hypochlorite (Ca(ClO)2) tablets for making swimming pool chlorine. I think calcium hypochlorite would be more effective than using sodium hypochlorite (NaClO) bleach because you can make a stronger solution than what is available as bleach in the store. Also, as I mentioned earlier, because it has sodium hydroxide (NaOH) added as a preservative, household bleach has a ph of over 12 and requires the addition of an acid to bring it down to a lower ph.

Let me know what you find out about these tablets. I'm still waiting for my ph meter to show up so I can begin experimenting with NaClO and HCl.

*NOTE*

Additional research has proven me wrong about calcium hypochlorite making a solution near neutral in ph. In truth, a 1% solution of calcium hypochlorite in water has a ph of up to 10.8. It makes sense; if the solution was at a ph of 7, it would be hypochlorous acid instead of calcium hypochlorite.


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## Barren Realms 007

For the small pool tablets they are 99% Trichlor-S-Triazinetrine.

http://www.intheswim.com/Pool-Chemicals/Pool-Chlorine-and-Bromine/1-Inch-Chlorine-Tablets/

Or you can go with the large ones that are 79%.

http://www.intheswim.com/Pool-Chemicals/Pool-Chlorine-and-Bromine/Triple-Action-Chlorine-Super-Skimmer-Tabs/

Graular chlorine Contains premium-quality 56% available stabilized chlorine. 99% Sodium Dichloro-S-Triazinetrione Dihydrate.

http://www.intheswim.com/Pool-Chemicals/Pool-Chlorine-and-Bromine/Granular-Chlorine/

But don't mix the granular and the tablets together in an inclosed container.

I have used the granular chlorine in some applications but have not used the tablets.

They are desighned the dissolve in the water and mix the chlorine with the water.


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## Traveller11

Barren Realms 007 said:


> For the small pool tablets they are 99% Trichlor-S-Triazinetrine.
> 
> http://www.intheswim.com/Pool-Chemicals/Pool-Chlorine-and-Bromine/1-Inch-Chlorine-Tablets/
> 
> Or you can go with the large ones that are 79%.
> 
> http://www.intheswim.com/Pool-Chemicals/Pool-Chlorine-and-Bromine/Triple-Action-Chlorine-Super-Skimmer-Tabs/
> 
> Graular chlorine Contains premium-quality 56% available stabilized chlorine. 99% Sodium Dichloro-S-Triazinetrione Dihydrate.
> 
> http://www.intheswim.com/Pool-Chemicals/Pool-Chlorine-and-Bromine/Granular-Chlorine/
> 
> But don't mix the granular and the tablets together in an inclosed container.
> 
> I have used the granular chlorine in some applications but have not used the tablets.
> 
> They are desighned the dissolve in the water and mix the chlorine with the water.



Interesting. I wonder if they end up producing hypochlorous acid once dissolved.

Once I get my ph meter and get the experiment up and running, I'll purchase some of these tablets and see if they are reactive with gold.

Happy New Year!


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## Traveller11

Hi Realms

I did a little searching and found this site:

http://www.stabilised-chlorine-tablet.co.uk/

The formula for this compound, trichloro-s-triazinetrione (trichloroisocyanuric acid), is C3Cl3N3O3 and this article states that, when mixed with water, the chlorine becomes hypochlorous acid. It does have a tendency to lower ph as it also produces isocyanuric acid, which may or may not be a good thing, depending on what my experiments turn up.

The only disadvantage I can see is the slow release thing. It might be just as easy to buy dry calcium hypochlorite and mix it with water, again giving us the hypochlorous acid.


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## Traveller11

Interesting article about the hypochorous acid <--> hypochlorite shift (HOCl <--> OCl) that is mandated by the ph of the chlorine solution.

http://www.poolhelp.com/HOCI_OCI.aspx

As HOCl is the most active oxidiser of the two (80-120 x more so than OCl) it is desirable to maximise the HOCL, which happens at a ph of 5 (see chart on link). However, as ph 5 is acidic, it may be necessary to compromise for a lower percentage of HOCl, by raising the ph closer to 7, to avoid the release of chlorine gas and the dissolving of iron and its oxides at the lower ph's.


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## Traveller11

Chlorination. I - from the "Australian Town and Country Journal (NSW)" January 31, 1891

The chlorination process of extracting gold From its matrix, and from from concentrates, is freely alluded to in newspapers and amongst miners; and yet, as a rule, the principle is but vaguely understood, even by men who make mining their business. Our explanation will be principally for persons who understand but little, if anything, of chemistry. To the scientific man, the great affinity of chlorine for the precious metals has been known almost ever since the distinguished German chemist, Schule, first discovered chlorine, about the year 1774. Chlorine, then, is an element, that is a simple substance, out of which nothing can be produced but itself. It is a gas, and has many remarkable properties- bleaching almost all colored substances, and being very heavy as compared with common air, and being also very deleterious to breathe. It is largely consumed by man and the lower animals in food as common salt, which contains a little more than half of pure chlorine. It conies into uso in mining in consequence chiefly of its great affinity or liking for gold and silver. If it can get sufficiently near it will seize hold of them, appropriating a certain portion to itself, making what is called chloride of gold ot silver. It being so abundant in nature, salt being so common, it is made cheaply-a little dilute sulphuric acid put on salt liberates chlorine gas, and its attraction for silver can be witnessed by the curious any day in the Sydney Mint by watching the chlorine gas being put into the bottom of the molten gold in the pot, and as it bubbles up to top seeing it seize hold of the silver, carrying it to the top of the gold as a chloride of silver. In using chlorine to extract gold you simply crush the stone or matrix so fine that it can get at the gold and take hold of it as a chloride. The easiest way to do this is to'put the chlorine in a solution in water, and so powerful is its action on gold that it dissolves that metal, holding it in
solution as water holds sugar. There is no difficulty in making a solution of chlorine, as at ordinary temperatures water dissolves about twice its volume of chlorine. Thus then having liberated the gold from the stone by crushing, and having made chlorine gas, as can be done cheaply, say from common salt, and having passed the chlorine so made through water, and thus made a solution of chlorine, and bringing it and the crushed stone together, in a short time you have your chlorine solution, containing all the gold in solution that was in the crushed stone. Having then the auriferous chlorine solution decanted or run off from the sludge or crushed stone or pyrites, you put some thing into it which will deposit or throw down the gold. Either one of two things, both of them very cheap and easily obtained, will do this effectuality, viz., a solution of sulphate of iron, common green vitrol, or pieces of common wood charcoal. The first will throw all the gold down as a powder ; the other, wood charcoal, will take to itself the gold out of the solution as a brown film, and upon the charcoal being burned away the pure gold remains. This is the rationale or reason of what is called the chlorination process, and any person of ordinary capacity, upon reflecting upon the foregoing, will not fail to comprehend the method used through the aid of certain machinery, which we will presently describe. It may help to understand this subject if we remind the reader that each of the three chief processes of extracting gold from its matrix or stone or pyritous matter consists in bringing it into contact with some substance which has so great an affinity or liking for it that it is taken up or amalgamated, and then the amalgamating substance got rid of or the gold taken from it. Thus in the common stamper battery or grinding mill mercury is the amalgamat ing material, as all miners know, which takes up the gold. In smelting, matter containing gold is put by intense heat, often assisted by fluxes of various kinds, into a state of fusion, and then brought in contact with molten lead, which, like mercury, has an intense affinity for gold, and it is thus extracted-the lead in the one case and the mercury in the other being ultimately taken from the gold by evaporation, or as regards the lead by cupellation, which is in effect evaporation. As regards the third great process, viz., extracting by chlorine, we have explained upon what principle that is carried out, being, in fact, like the other two, merely making use of a substance which, by its great affinity, will seize hold of the gold and collect it, so to speak.
Of the three processes, the crushing and amalgamating with mercury, the smelting and amalgamating with lead, and the crushing and absorption by a solution of chlorine, each is suitable according to the way the gold is found in the stone or auriferous material. Rich pyrites or black sand, or concentrates, require smelting as a rule, because all the grinding, to whatever degree of fineness it may be carried, will not liberate all the gold from the iron and metals, so that mercury can act on it." Again, crushing by stampers or grinding in mills will be suitable where much of the gold is fairly coarse, and, as it is called, free in the stone. Arid chlorination comes in and is useful where gold is free in the stone, but is so very fine that in crushing in the ordinary way the mercury can't take hold of it but is carried away in the sludge or tailings. Chlorination also is useful in extracting the precious metal from concentrates, though in this case it may be found more suitable to sell them to the smelting works than to treat them by
chlorine at the mine.
Having thus described what may be termed the principles of chlorination, we now describe the appliances by which they are carried into effect. First, the stone is crushed dry, arid, as in the case of the iron-clad reef at Cargo where chlorination is carried on, by heavy steel rollers driven by steam power. Next the crushed stone is calcined in anordinary reverberatory calcining furnace to eliminate all the sulphur and arsenic which it is advisable to get rid of before treatment by chlorine. Then the calcined crushed stone is put into a large iron barrel about 8 ft long by about 3 ft in diameter* and lined with lead, because chlorine acts powerfully on iron as it does on gold and silver, but will not touch lead. 

On page 25

A sufficient quantity of water is put in the barrel to make a thin sludge, then a quantity of chloride lime-that stuff much used as a disinfectant, and which is simply common lime saturated with chlorine gas-is put to the sludge, and upon that a small quantity of sulphuric acid. The barrel is then closed down air-tight, and made to
revolve very slowly. The acid acting on the lime evolves the chlorine, which is taken up by the water, and the chlorine solution takes up the gold in the stone. After some hours of the barrel revolving, the whole contents are turned out into
a cask or receptacle and allowed to settle. The clear liquor is then drawn off, and made to pass through a cask or vessel partly packed with common wood charcoal, which, as the auriferous chlorine solution passes through it, takes the gold
to itself; and upon tho charcoal being burned away, say in an iron pot, the pure gold remains. , This, then, is the chlorination process, which, we
think; our readers-even those quite unacquainted with chemistry-will clearly comprehend.


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## Traveller11

Found this on the Clorox site:

What’s in Clorox® Regular Bleach?

Ingredients that make up one percent or more of the contents of a product by weight are listed in descending order of concentration. Those that make up less than one percent — like fragrances, dyes and preservatives — are listed in alphabetical order.


Water

Sodium hypochlorite

Sodium chloride

Sodium carbonate

Sodium hydroxide

Sodium polyacrylate

--------------------------------------------------------------------------------------

From this list and the preamble to it, we can deduce that sodium hydroxide (NaOH) makes up less than 1% of the weight of a solution of bleach. The sodium carbonate is slightly basic and would contribute to the high ph of a bleach solution, as well.

If one unit of added hydrochloric acid (HCl) would neutralize one unit of NaOH according to the following formula:

NaOH + HCl = NaCl + H2O

and, using regular 34% muriatic acid for HCl it was a one to one tradeoff (it may be necessary to dilute the HCl to a much lower percentage while trying to establish the needed volume), in a litre of bleach it might require as little as 2 to 3 millilitres of HCL to adjust the ph to the desired 7-7.5.

I must say I am quite surprised that less than 1% NaOH in a bleach solution is sufficient to maintain the ph of the bleach over 12.


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## Barren Realms 007

If you have a PH meter and do some testing you will be surprised how little of an amount of solution it takes to change the PH.


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## Traveller11

I'm patiently waiting for the ph meter I ordered on Ebay to arrive in the mail. I look forward to using it when it arrives.

Thinking over what you said, I looked again at one of the 1890's recipes for making a gold leaching chlorine solution. In this case, chlorine gas was introduced into a cylinder containing ground ore and water. Following, compressed air was introduced to a pressure of 60 psi, dissolving Cl2 gas in the water.

Once dissolved, the following happened:

Cl2 + H2O = HOCl + HCl

I had assumed the HCl produced would be of such low volume as to not alter the ph of the water (assumed to be 7) much below 5-6 but, I am not so sure anymore. Any ideas?

I know, from reading these older papers, that there was not much worry of the chlorine solutions dissolving iron (instead of gold) from iron oxides and, for this reason, I have to assume the ph of their chlorine solutions was not overly acidic. This, they claim, was one of the reasons for roasting ores; to convert iron and other base metals into oxides that would be impervious to their chlorine solution. Accordingly, it takes a very low ph (1-2?) to break the bond between the base metal and the oxygen.

This information is in contrast to an experiment I did with a sample of magnetite sand (Fe3O4). In a plastic container, I covered the magnetite with 1/2" of HCl. Within seconds, the HCl turned a dark amber colour; indicating I had made ferric chloride (FeCl3).


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## butcher

Traveller11,

I am not sure what you are working towards here,or where you are at, but figured I would add a thought and some equation’s I stole from Wikipedia.

Chlorine in water forms Hypochlorous acid and hydrochloric acid
Cl2 + H2O <--> HOCl +HCl
Notice the above reaction is reversible
HOCl + HCl <--> Cl2 +H2O

In acid Hypochlorous acid forms chlorine gas and water (remember the Chlorine gas reacts with metals to form metal chlorides or escapes the solution)
HCL + HOCl -->H2O +CL2 (gas) 

Light or metal oxide’s (like copper oxide can break down the chlorine also
2Cl2 + H2O ---light--> 4HCl + H2O
(If copper oxide we would get copper chlorides)

Common Bleach sodium hypochlorite NaClO is a sodium salt of Hypochlorous acid HOCl
There are a couple ways bleach is made electrolysis of salt brine or chlorine gas dissolved in cold sodium hydroxide, both will contain salt NaCl and be caustic with NaOH (the caustic helps to keep chlorine gas in solution dissolved in the water) household bleach sodium hydroxide is mostly water around 92 to 97% H2O.

Cl2 +2 NaOH --> NaCl +H2O + NaClO

NaOH can help to keep the chlorine in the water as a basic solution, and as we know acid and a metal base will form a salt of that metal:
HCl + NaOH --> NaCl + H2O

Sodium hypochlorite and acid can form chlorine gas:
NaClO + HCl --> NaCl + H2O + CL2 (gas)

Now we also need to consider the sodium hypochlorite is actually a basic solution of salt and sodium hypochlorite and sodium hydroxide so adding acid not only generates chlorine gas which reacts with metals or escapes as gas from solution, the reaction of the base and acid also brings pH closer to neutral as well as forming more salts and water in solution.

As we stated bleach can me mostly water which can dilute an acidic solution as well as act to adjust it pH toward neutral forming salts of our acid as the chlorine gases off or reacts with metals in solution to form metal chlorides.

Also if bleach is heated or evaporated from solution it can form salts of sodium chloride NaCl and sodium chlorate's NaClO3.

Bleach and hydrogen peroxide give off oxygen and form chlorine gas and salt water
4NaClO + 2H2O2 --> 4NaOH + 2Cl2 +O2 
(again we see where this would be adjusting pH of our acidic solutions)

So with this we can see how these solutions not only dilute our acid but also can work to neutralize it forming a lot of salt in solution as the chlorine or other gases react or escape from the leach solution,

Many bleach solutions also dilute the leach.
Alternatives are dry bleach powders or using gases to do the same job without the side reactions.

Iron hydroxide is very un-reactive; to acids the red rouge powder is almost impossible to dissolve into acid, you can dissolve gold from this red powder and not dissolve the iron or put it into solution (as an iron chloride) even with acids as strong as aqua regia, roasting techniques are very important steps, your goal is to remove sulfides and other unwanted compounds and convert the oxide or iron compounds to the most desirable state for your next leach, if we are leaching iron first we want the iron to go into solution, but in a chlorination of acid solution where your trying to leach gold were too much iron in solution would re-precipitate the leached gold and put iron into solution ,with gold depending on conditions, we would not want the iron is a state easily dissolved.
How you roast can help quite a bit of what state the iron is in, also most of the soluble iron can also be leached before going after the gold.

But concentrating the of the ore down to a very high percentage of gold to ore or base metals is also important, as you not only will have more trouble and cost and waste, trying to process a low gold to ore or base metal ratio your loses will be higher and the likelihood of success is reduce with the more ore or base metals involved.

As I said I am not sure where you are at on this or if this will even help any.


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## modtheworld44

butcher said:


> Traveller11,
> 
> I am not sure what you are working towards here,or where you are at, but figured I would add a thought and some equation’s I stole from Wikipedia.
> 
> Chlorine in water forms Hypochlorous acid and hydrochloric acid
> Cl2 + H2O <--> HOCl +HCl
> Notice the above reaction is reversible
> HOCl + HCl <--> Cl2 +H2O
> 
> In acid Hypochlorous acid forms chlorine gas and water (remember the Chlorine gas reacts with metals to form metal chlorides or escapes the solution)
> HCL + HOCl -->H2O +CL2 (gas)
> 
> Light or metal oxide’s (like copper oxide can break down the chlorine also
> 2Cl2 + H2O ---light--> 4HCl + H2O
> (If copper oxide we would get copper chlorides)
> 
> Common Bleach sodium hypochlorite NaClO is a sodium salt of Hypochlorous acid HOCl
> There are a couple ways bleach is made electrolysis of salt brine or chlorine gas dissolved in cold sodium hydroxide, both will contain salt NaCl and be caustic with NaOH (the caustic helps to keep chlorine gas in solution dissolved in the water) household bleach sodium hydroxide is mostly water around 92 to 97% H2O.
> 
> Cl2 +2 NaOH --> NaCl +H2O + NaClO
> 
> NaOH can help to keep the chlorine in the water as a basic solution, and as we know acid and a metal base will form a salt of that metal:
> HCl + NaOH --> NaCl + H2O
> 
> Sodium hypochlorite and acid can form chlorine gas:
> NaClO + HCl --> NaCl + H2O + CL2 (gas)
> 
> Now we also need to consider the sodium hypochlorite is actually a basic solution of salt and sodium hypochlorite and sodium hydroxide so adding acid not only generates chlorine gas which reacts with metals or escapes as gas from solution, the reaction of the base and acid also brings pH closer to neutral as well as forming more salts and water in solution.
> 
> As we stated bleach can me mostly water which can dilute an acidic solution as well as act to adjust it pH toward neutral forming salts of our acid as the chlorine gases off or reacts with metals in solution to form metal chlorides.
> 
> Also if bleach is heated or evaporated from solution it can form salts of sodium chloride NaCl and sodium chlorate's NaClO3.
> 
> Bleach and hydrogen peroxide give off oxygen and form chlorine gas and salt water
> 4NaClO + 2H2O2 --> 4NaOH + 2Cl2 +O2
> (again we see where this would be adjusting pH of our acidic solutions)
> 
> So with this we can see how these solutions not only dilute our acid but also can work to neutralize it forming a lot of salt in solution as the chlorine or other gases react or escape from the leach solution,
> 
> Many bleach solutions also dilute the leach.
> Alternatives are dry bleach powders or using gases to do the same job without the side reactions.
> 
> Iron hydroxide is very un-reactive; to acids the red rouge powder is almost impossible to dissolve into acid, you can dissolve gold from this red powder and not dissolve the iron or put it into solution (as an iron chloride) even with acids as strong as aqua regia, roasting techniques are very important steps, your goal is to remove sulfides and other unwanted compounds and convert the oxide or iron compounds to the most desirable state for your next leach, if we are leaching iron first we want the iron to go into solution, but in a chlorination of acid solution where your trying to leach gold were too much iron in solution would re-precipitate the leached gold and put iron into solution ,with gold depending on conditions, we would not want the iron is a state easily dissolved.
> How you roast can help quite a bit of what state the iron is in, also most of the soluble iron can also be leached before going after the gold.
> 
> But concentrating the of the ore down to a very high percentage of gold to ore or base metals is also important, as you not only will have more trouble and cost and waste, trying to process a low gold to ore or base metal ratio your loses will be higher and the likelihood of success is reduce with the more ore or base metals involved.
> 
> As I said I am not sure where you are at on this or if this will even help any.



butcher

I think Traveller11 is wanting a way to generate the wet chlorine gas,so he can use it for ore leaching.I'm not 100% sure on that so please don't quote me on it.

If this is the reason then this needs to be looked at more carefully,it's a piece of the page that Traveller11 posted the link for up in his second post on this page.

The full equation may be represented like this:
Cl2 + H2O --> HOCl + HCl
HOCl --> OCl– + H+
HOCl is, of course, the “active ingredient”. The OCl– is a bank, or reservoir of less active chlorine.
A common pool industry myth is that when HOCl is used in a pool only OCl– remains. In reality, when HOCl is used, OCl– immediately converts back to HOCl to maintain the percentage division mandated by the pH.
Although the actual reactions in water may be complex, a few illustrations in simplified language may help to describe what happens.
For example, if a pool contained 3 ppm total chlorine at a pH of 7.5, there would be about 1.5 ppm HOCl and 1.5 OCl–. If 1 ppm chlorine demand is introduced into the water, the myth would have us believe that as the demand is met, the HOCl is lowered to 0.5 ppm with the OCl– remaining at 1.5 ppm. Assuming the pH to be unchanged, what actually happens is that the total chlorine is lowered to 2 ppm, the HOCl is lowered to 1 ppm, and the OCl– is lowered to 1 ppm. This happens even though it may have actually been only the faster and more potent HOCl that satisfied the chlorine demand. The subsequent shift of 0.5 OCl– to HOCl is virtually instantaneous.


The demand in his case would be ores,so basically it would keep generating chlorine wet gas until all the OCl- was shifted to HOCl.

This is why I use Bleach in my GEOMOD cell.I rejuvenate the chlorine by adding pool chlorine tablets and the anode turns the chlorine into gas,which eats the metals.So in theory this cell could do the same for ores.I plan to try ore in my cell real soon.If you haven't read the full article yet you should it might give you better insite on what he's wanting to do.I've read and reread it about 5-6 times now.Hope this adds something to the forum that is of use!



modtheworld44


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## Traveller11

Hello modtheworld44

I think we are working towards the same end but have slightly different interpretations of what is happening. Looking at some of these articles from the 1890's, I do not believe that producing chlorine gas in the presence of ore is what they were doing. Yes, the one process fed Cl2 gas into the cylinder with ore and water in it but, it was then immediately dissolved in the water and transformed into HOCl and HCl. I also believe this did not lower the ph of the water significantly and, if it was 7 to start with, would only be slightly lower than this with the Cl2 dissolved in it.

In other words, I believe these old timers ended up with a strong solution of hypochlorous acid/sodium hypochlorite in water with perhaps minute amounts of Cl2 gas being released. The evidence I give for this is that they did not bother trying to remove iron oxides such as magnetite and hematite from the ores prior to leaching. If this were attempted with the normal HCl/Clorox formula proscribing large amounts of HCl added to Clorox, the solution would be so acidic, it would break the bonds of the oxides and put iron into solution instead of gold.

It seems the oldtimers were dissolving gold with an almost neutral solution of HOCl/NaClO in water that, except for strength, differed very little from swimming pool water.


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## modtheworld44

Traveller11 said:


> Hello modtheworld44
> 
> I think we are working towards the same end but have slightly different interpretations of what is happening. Looking at some of these articles from the 1890's, I do not believe that producing chlorine gas in the presence of ore is what they were doing. Yes, the one process fed Cl2 gas into the cylinder with ore and water in it but, it was then immediately dissolved in the water and transformed into HOCl and HCl. I also believe this did not lower the ph of the water significantly and, if it was 7 to start with, would only be slightly lower than this with the Cl2 dissolved in it.
> 
> In other words, I believe these old timers ended up with a strong solution of hypochlorous acid/sodium hypochlorite in water with perhaps minute amounts of Cl2 gas being released. The evidence I give for this is that they did not bother trying to remove iron oxides such as magnetite and hematite from the ores prior to leaching. If this were attempted with the normal HCl/Clorox formula proscribing large amounts of HCl added to Clorox, the solution would be so acidic, it would break the bonds of the oxides and put iron into solution instead of gold.
> 
> It seems the oldtimers were dissolving gold with an almost neutral solution of HOCl/NaClO in water that, except for strength, differed very little from swimming pool water.



Traveller11

The point I'm trying to make is this,back in the old days bleach wasn't called bleach.What did they call it I'm not sure,but if I had to guess chlorine .They didn't use hcl with it because there was no need.

What do you smell the secant you open a bottle of bleach?
What is your guess as to why they pressurized the tank?
Why didn't they need hcl?

These are all the questions I have asked my self.



modtheworld44


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## Traveller11

From "The Chemistry of Gold Extraction" by John O. Marsden, C. Iain House

"An atmospheric leaching process using NaCl and NaOCl at ph 7 was developed by ISL Ventures in the late 1980's as an option for gold ores containing cyanide-soluble copper, because base metals are not leached under these conditions in this system. The use of isocyanuric acid (2,4,6 trihydroxy-s-triazine) was proposed to reduce the rate of consumption of the oxidant (ie. ClO- species, supplied by the NaOCl). Gold recoveries in excess of 80% were reported for several gold ores when NaOCl concentrations of 1 to 2 gm./litre were employed; however, high NaOCl consumptions (.5 to 1.0 kg./ton of ore) hamper the commercialization of the process."


This author refers to chlorine leaching in his book as a "chlorine/chloride" process with the chlorine being supplied, in its various shifting ph mandated forms, as hypochlorite, hypochlorous acid or chlorine gas. I was a bit puzzled as to the "chloride" part until I remembered that hydrochloric acid is also referred to as "hydrogen chloride" and is, indeed, a chloride. It appears that the inventors at ISL Ventures, in order to maintain a ph of 7, have traded the chloride HCl for the chloride NaCl.


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## Traveller11

Quote from modthe world:
Traveller11

The point I'm trying to make is this,back in the old days bleach wasn't called bleach.What did they call it I'm not sure,but if I had to guess chlorine .They didn't use hcl with it because there was no need.

What do you smell the secant you open a bottle of bleach?
What is your guess as to why they pressurized the tank?
Why didn't they need hcl?

These are all the questions I have asked my self.

-------------------------------------------------------------------------------------

There was a product, marketed in the late 1800's, called Dupont Mining Salts that was used by miners to leach gold from ores. Very little is known about it, as it has not been made in 100 years, but it is felt that it was powdered calcium hypochlorite and that it would make calcium hypochlorite bleach when dissolved in water. As calcium hypochlorite will make a solution with a pH 0f about 10.5 when dissolved in water, it is necessary to lower the pH to convert the hypochlorite ion into the oxidizer hypochlorous acid. However, no information is available to show this was done or what pH the solution would have to be lowered to in order to leach gold and only gold.

When I open a bottle of sodium hypochlorite bleach, I smell bleach and only bleach. With the pH of bleach at +12, chlorine gas cannot escape from solution.

The tank was pressurized to make chlorine gas dissolve in water. Once dissolved, a goodly portion of it becomes hypochlorous acid and hydrochloric acid.

I believe the reason they didn't add HCl was because they were not trying to lower the pH of the bleach solution anywhere near as much as the currently popular HCl/Clorox leach method does. While gold will go into solution at extremely low pH's, iron oxides will also release iron and put it into solution at very low pH's, as well. This is why the promoters of the modern HCl/Clorox method, with a 4:1 ratio of HCl to Clorox, insist that all forms of iron be removed from your ore prior to leaching. The method practiced by these oldtimers reputedly operated at pH's of from 3 to 8. They made no effort at all to remove iron from their ores prior to leaching. They did, however, roast their ores to convert iron sulphides and other forms of iron to oxides. As I quoted a few posts back, converting to iron oxides made the iron impervious to their chlorine leaching solutions. This fact alone proves to me their chlorine solutions were nowhere near as acidic as the modern HCl/Clorox method, as it requires an acidic solution of 1-2 pH to break the bonds of the oxides.

As most of us are dealing with iron oxides in our ores (black sand) there is no reason to roast our ores. Even the sulphides stand a good chance of not being touched by a chlorine solution with a pH of +3.

From "The Chemistry of Gold Extraction" by John O. Marsden and C. Iain House:

"Below pH 3, pyrite is attacked and dissolved in aqueous chloride solution using chlorine as the oxidant. However, between about pH 3 and 6, with hypochlorous species as the oxidant, the dissolution rate of pyrite is greatly reduced. One investigation has shown that the dissolution rate is reduced by a factor of four as the pH is increased from 2 to 4, and by a similar factor again when the pH is increased from 4 to 6. This presents an interesting process option for ores containing free gold with barren pyrite gangue, with the potential for selective gold dissolution above about pH 3."

While it will be necessary to lower the pH of a bleach solution (10.5-12), my research shows that, for a litre of solution, it may take only 1 or 2 (or less) millilitres of HCl to bring the pH of the bleach solution to the desired range of 5-7.5. It also appears now that it may help to add salt (NaCl) to the solution as a source of chloride. According to "The Chemistry of Gold Extraction", bringing the volume of NaCl in chlorine solution to over 3% will accelerate the dissolution process considerably.


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## butcher

Traveller11,
I have read about and tried it both ways.

Using HCl as the main ingredient of solution, and adding small amounts of NaClO, to generate chlorine and other compounds to dissolve gold.
And
Using NaClO and adding small amounts of HCl, to generate chlorine and other compounds to dissolve gold, which also works.

The latter I did notice in several researches where they were using this method to process Ore.

I just assumed it to be the same process only done backwards, with both methods just generating chlorine to oxidize and dissolve gold.

They both worked to dissolve gold, but I never thought of why they might choose the later process.

It sounds like maybe you have stumbled onto (or may have figured out) an explanation of why they would use this process, instead of the top method we normally discuss on the forum, your theory is making a lot of sense, dissolving gold with chlorine generation while keeping pH in a state to minimize attack of Iron and to help keep it from going into solution as much as possible.

Very interesting.


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## Traveller11

Thank you, butcher. It means a lot to me to hear encouraging words from you.

The words "stumbled onto" are probably the most correct. A while back, I was feeling somewhat frustrated at the prospect of having to remove all the iron oxides (black sand) from my concentrates, prior to leaching with HCl/Clorox, and, while looking for a good way to do this, just happened onto james122964's post about leaching with HCl/Clorox. He was quite adamant about "cutting way back" on the HCl and claimed that, with far less HCl in the solution, the black sands were barely touched in the leaching process while the gold went into solution easily.

When starting with sodium hypochlorite, I am really beginning to wonder if Cl2 is generated at all, if the pH of the bleach solution never falls below 5. I am starting to think it may become hypochlorous acid and that it is this HOCl doing the work.

As I related a couple of posts back, I studied an excerpt from "The Chemistry of Gold Extraction" by John O. Marsden. The part that interested me was a leaching process using NaCl and NaOCl at pH 7, with no mention of HCl being added. This process was developed in the 1980's by ISL Ventures for the express purpose of dealing with ores containing cyanide-soluble copper because "base metals are not leached under these conditions in this system". If this were true, can you imagine the implications here, not just for small miners such as myself dealing with oxide rich ores, but for refiners as well? As I stated in the previous post, Mr. Marsden refers to chlorination as a "chlorine/chloride" process, with the hypochlorite/hypochlorous contribution presumably being the "chlorine" component. I then assumed NaCl to be the "chloride" component and wondered how HCl fit into things, until I recalled that another name for HCl is hydrogen chloride and it is, indeed, a chloride.

I took the very bold step of emailing Mr. Marsden (can't say where I found his email address) to ask him if he would be amenable to answering a few questions in order to help set a small time miner on the right path. I hope he has the time to answer, as he is quite a prestigious man and is on many corporate boards and consults mining operations worldwide.


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## butcher

I do hope you can have a discussion with Mr. Marsden, I would also be very interested in what you learn.

I do not know enough chemistry to say whether Hypochlorous acid and that it is this HOCl doing the work or not, whether it would be a strong enough oxidizer to oxidize gold.

From the way I understand it we need a strong enough oxidizer to oxidize the gold, and free chlorides in solution for the oxidized gold to attach on to and form the gold chloride soluble in solution.

Hypochlorous acid HOCl being a weak acid, but also a strong oxidizer, strong enough to oxidize sulfides.

2FeS2 + 15HOCl + 7H2O --> 2Fe(OH)3 +2H(+) +SO4(-) + 15Cl(-)
Note insoluble iron hydroxide (which will not dissolve easily), and free hydrogen and chlorides!

I could not find direct evidence where any one directly says that gold will oxidize in HOCl, but they do use it as an oxidation agent with cyanide (suggesting it will be strong enough to oxidize the gold).

The fact that with chlorine in very acidic conditions where gold is oxidized by chlorine, and also noting that HOCl can also be in a solution with chlorine, at fairly low pH, with about pH one, and that it looks like a solution could be a mix of chlorine and hypochlorite, and at a slightly higher pH where gold will still dissolve, but chlorine content can be very low or possibly not in solution with HOCl, suggests to me that in fact HOCl may be a very effective oxidizing agent for gold, if this is fact then all we need is some anion in solution like chlorides for the oxidized gold to attach to, to be able to dissolve the gold into solution.

Of course most of this is somewhat speculation on my part, but it looks like the reaction of iron sulfide could actually somewhat helpful, the reaction, forming insoluble iron hydroxide and possibly helping to put gold into solution.

But then again I could also be like a old blind coon hound here, and just barking up the wrong tree,


http://www.freepatentsonline.com/4662938.pdf
electrolysis oxidation
http://cdn.intechopen.com/pdfs/27212/InTech-Electrooxidation_as_a_pretreatment_process_before_cyanidation.pdf


----------



## modtheworld44

butcher and Traveller11

Here's some explanation on why they call bleach Bleach.

http://en.wikipedia.org/wiki/Bleach

When you open bleach you do smell chlorine. 
Please read the above and below articles in their entirety,yes some of it is boring but it should shine some light on this thread.

This article is on chlorine and theres a table of it's oxidized states that yall should look at.Remember reading is fundamental. :mrgreen: 

http://en.wikipedia.org/wiki/Chlorine

This is a great conversation we're in here and I enjoy shooting theories back and forth.If yall guys would make a small GEOMOD CELL yall would see what your wanting to see happen.Thanks for your time.


modtheworld44


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## Traveller11

From "Advances in Gold Ore Processing" by M.D. Adams:

"Pre-treatment of carbonaceous or sulfidic ores by roasting or pressure oxidation is normally required prior to chlorine or bromine leaching to render ores relatively inert, and consequently reduce reagent consumption. For example, the selective recovery of gold and silver was carried out recently by Puvvada and Murthy from a chalcopyrite concentrate. Gold and silver grades in the concentrate were 11 and 140 g/t, respectively. Laboratory-scale tests were conducted at room temperature on 20% solids slurry containing 25 g/L NaOCl and 0.35 M HCl. Increasing the NaCl concentration increased the rate as well as the extent of gold and silver extraction. Gold and silver recoveries of 42.7 and 45.0%, respectively, were obtained with 200 g/L NaCl. Dissolution of silver was found to be independent of NaOCl concentration. However, pressure oxidizing the copper concentrate and then leaching with NaOCl concentration of 25 g/L, 200 g/L NaCl and 0.35 M HCL for one hour resulted in gold and silver recoveries of 90.0 and 92.5%, respectively."


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## Traveller11

butcher said:


> I do hope you can have a discussion with Mr. Marsden, I would also be very interested in what you learn.
> 
> I do not know enough chemistry to say whether Hypochlorous acid and that it is this HOCl doing the work or not, whether it would be a strong enough oxidizer to oxidize gold.
> 
> From the way I understand it we need a strong enough oxidizer to oxidize the gold, and free chlorides in solution for the oxidized gold to attach on to and form the gold chloride soluble in solution.
> 
> Hypochlorous acid HOCl being a weak acid, but also a strong oxidizer, strong enough to oxidize sulfides.
> 
> 2FeS2 + 15HOCl + 7H2O --> 2Fe(OH)3 +2H(+) +SO4(-) + 15Cl(-)
> Note insoluble iron hydroxide (which will not dissolve easily), and free hydrogen and chlorides!
> 
> I could not find direct evidence where any one directly says that gold will oxidize in HOCl, but they do use it as an oxidation agent with cyanide (suggesting it will be strong enough to oxidize the gold).
> 
> The fact that with chlorine in very acidic conditions where gold is oxidized by chlorine, and also noting that HOCl can also be in a solution with chlorine, at fairly low pH, with about pH one, and that it looks like a solution could be a mix of chlorine and hypochlorite, and at a slightly higher pH where gold will still dissolve, but chlorine content can be very low or possibly not in solution with HOCl, suggests to me that in fact HOCl may be a very effective oxidizing agent for gold, if this is fact then all we need is some anion in solution like chlorides for the oxidized gold to attach to, to be able to dissolve the gold into solution.
> 
> Of course most of this is somewhat speculation on my part, but it looks like the reaction of iron sulfide could actually somewhat helpful, the reaction, forming insoluble iron hydroxide and possibly helping to put gold into solution.
> 
> But then again I could also be like a old blind coon hound here, and just barking up the wrong tree,
> 
> 
> http://www.freepatentsonline.com/4662938.pdf
> electrolysis oxidation
> http://cdn.intechopen.com/pdfs/27212/InTech-Electrooxidation_as_a_pretreatment_process_before_cyanidation.pdf




LOL Even an old hound gets the scent right every once in a while. :mrgreen:


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## okieminer

Im new to this but Im trying to leach ore with chlorine and hci. My ore has been assayed at 2+ O/T. I have crushed it and ran it over a RP-4 table and have panned it also with no visible gold. Would like to know a possible mix using bleach or swimming pool chlorine. And if you can use sodium bisulfate to take the gold solution back to a powder. Can someone please help me by giving me a mix ratio as in 2 cups of this to 1 cup of this. I know that is really basic but that is what I need. Thank you


----------



## Traveller11

okieminer said:


> Im new to this but Im trying to leach ore with chlorine and hci. My ore has been assayed at 2+ O/T. I have crushed it and ran it over a RP-4 table and have panned it also with no visible gold. Would like to know a possible mix using bleach or swimming pool chlorine. And if you can use sodium bisulfate to take the gold solution back to a powder. Can someone please help me by giving me a mix ratio as in 2 cups of this to 1 cup of this. I know that is really basic but that is what I need. Thank you



What I am about to give you has not been proven by me yet, although it is the best interpretation of methods from the 1890's I can make.

Pour liquid Clorox bleach (6%) into a container, or mix calcium hypochlorite powder (pool chlorine) and water to get a stronger hypochlorite solution. A 15% solution of calcium hypochlorite should be sufficient.

Wearing acid resistant gloves and clothing, respirator with cartridges to filter chlorine gas and safety glasses or face shield, begin adding tiny amounts of HCl to bleach. Be careful, as there will be some reaction as acid meets base. Between additions of HCl, test the pH of the solution with a pH meter. Slowly but surely bring the pH down to 7.5. At pH 7.5, about 50% of the hypochlorite will have become hypochlorous acid (HOCl). If you do not allow the solution to become acidic (- pH 7), chlorine gas production should be kept to a minimum and will not be detectable. However, under pH 5, great amounts of chlorine gas will be made.

Once the pH is at 7.5, stop adding HCl. At this point, add either sodium chloride or calcium chloride to about 20% of volume. Stir until dissolved. The actual amount of these chlorides is not critical as long as there is enough chloride present to put all of your gold into solution.

You must now have a plastic cylinder capable of holding your ground ore. Any copper or iron in your material that is not tied up as an oxide will spoil this process. This applies to any metal fittings on the cylinder, as well, as they will react with chlorine. The cylinder must be capable of being completely filled with chlorine solution, completely expelling any air inside the cylinder. Any large airspace inside the cylinder will allow the oxygen in the HOCl to be lost, making it into HCl and lowering the pH of the solution. An alternative is to pump air, through plastic fittings, into the cylinder until a pressure of 60 psi is obtained. This will also keep the HOCl from derading to HCl but requires a much sturdier cylinder capable of withstanding this elevated pressure. Remember, no metal in contactwith chlorine solution unless that metal is lead or titanium.

There must be a way of revolving this cylinder to keep all of the ore in contact with the chlorine solution during the period of leaching. Plastic bars lengthwise inside the cylinder will help to keep the ore mixed with the solution, something like the clay breaking bars inside a trommel keep things moving.

Once all this is done, revolve the cylinder for four hours, then open the cylinder and immediately (before the pH begins to drop) filter liquid to remove any ore solids. Wash ore with spray to recover any solution holding gold. Gold can then be precipitated from solution using sodium metabisulphite (not sodium bisulphate) or ferrous sulphate.


I am at the stage of building a small test unit from 4" ABS plumbing fittings and a 1/2" PVC ball valve. After that comes a platform with rollers on it where the cylinder can be driven by a belt from an electric motor. Although it looks simple, it gets quite complicated, and the real challenge will be scaling this up to a unit capable of processing 20 gallons at a time.

Please keep notes on anything you do and, if you discover anything worthy of note, I would appreciate your sharing this information.

Good luck!


----------



## Traveller11

okieminer said:


> Im new to this but Im trying to leach ore with chlorine and hci. My ore has been assayed at 2+ O/T. I have crushed it and ran it over a RP-4 table and have panned it also with no visible gold. Would like to know a possible mix using bleach or swimming pool chlorine. And if you can use sodium bisulfate to take the gold solution back to a powder. Can someone please help me by giving me a mix ratio as in 2 cups of this to 1 cup of this. I know that is really basic but that is what I need. Thank you



What I am about to give you has not been proven by me yet, although it is the best interpretation of methods from the 1890's I can make.

Pour liquid Clorox bleach (6%) into a container, or mix calcium hypochlorite powder (pool chlorine) and water to get a stronger hypochlorite solution. A 15% solution of calcium hypochlorite should be sufficient.

Wearing acid resistant gloves and clothing, respirator with cartridges to filter chlorine gas and safety glasses or face shield, begin adding tiny amounts of HCl to bleach. Be careful, as there will be some reaction as acid meets base. Between additions of HCl, test the pH of the solution with a pH meter. Slowly but surely bring the pH down to 7.5. At pH 7.5, about 50% of the hypochlorite will have become hypochlorous acid (HOCl). If you do not allow the solution to become acidic (- pH 7), chlorine gas production should be kept to a minimum and will not be detectable. However, under pH 5, great amounts of chlorine gas will be made.

It should be pointed out that, due to the instability of HOCl at atmospheric pressure, the above procedure should not be done until you are ready to use the HOCl.

Once the pH is at 7.5, stop adding HCl. At this point, add either sodium chloride or calcium chloride to about 20% of volume. Stir until dissolved. The actual amount of these chlorides is not critical as long as there is enough chloride present to put all of your gold into solution.

You must now have a plastic cylinder capable of holding your ground ore. Any copper or iron in your material that is not tied up as an oxide will spoil this process. This applies to any metal fittings on the cylinder, as well, as they will react with chlorine. The cylinder must be capable of being completely filled with chlorine solution, completely expelling any air inside the cylinder. Any large airspace inside the cylinder will allow the oxygen in the HOCl to be lost, making it into HCl and lowering the pH of the solution. By minimizing any airspace in the cylinder to almost nothing, only a small amount of oxygen lost from the HOCl will be sufficient to raise the pressure of that irspace higher than the maximum pressure at which HOCl can lose oxygen. An alternative is to pump air, through plastic fittings, into the cylinder until a pressure of 60 psi is obtained. This will also keep the HOCl from degrading to HCl but requires a much sturdier cylinder capable of withstanding this elevated pressure. Remember, no metal in contact with chlorine solution unless that metal is lead or titanium.

There must be a way of revolving this cylinder to keep all of the ore in contact with the chlorine solution during the period of leaching. Plastic bars lengthwise inside the cylinder will help to keep the ore mixed with the solution, something like the clay breaking bars inside a trommel keep things moving.

Once all of this is done, revolve the cylinder for four hours, then open the cylinder and immediately (before the pH begins to drop) filter liquid to remove any ore solids. Wash ore with spray to recover any solution holding gold. Gold can then be precipitated from solution using sodium metabisulphite (not sodium bisulphate) or ferrous sulphate. Test ore and solution with stannous chloride to make sure all gold is recovered.


I am at the stage of building a small test unit from 4" ABS plumbing fittings and a 1/2" PVC ball valve. After that comes a platform with rollers on it where the cylinder can be driven by a belt from an electric motor. Although it looks simple, it gets quite complicated, and the real challenge will be scaling this up to a unit capable of processing 20 gallons at a time.

Please keep notes on anything you do and, if you discover anything worthy of note, I would appreciate your sharing this information.

Good luck!


----------



## okieminer

Thank you for your help but when it comes to recovery about how much of the sodium metebisulphite do you use and do you use it in dry form or do you mix it with water.


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## Traveller11

http://www.youtube.com/watch?v=AHsPkoO4wKw


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## Traveller11

I have uncovered some fresh and relevant information regarding the chemistry behind this process. I am on my way out the door right now but will post this information tonight.


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## tcpoint

Been reading this thread with a lot of interest. Been waiting for the "fresh and relevant information" that you were going to post. Not trying to rush you or anything. I really appreciate the time you take sharing what you've learned.


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## ericrm

do someone know if gold chloride cement on base metal when solution is basic? could this work on gold plated pins?

edit: i missed that part...


Traveller11 said:


> You must now have a plastic cylinder capable of holding your ground ore. Any copper or iron in your material that is not tied up as an oxide will spoil this process. This applies to any metal fittings on the cylinder, as well, as they will react with chlorine.


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## Traveller11

tcpoint said:


> Been reading this thread with a lot of interest. Been waiting for the "fresh and relevant information" that you were going to post. Not trying to rush you or anything. I really appreciate the time you take sharing what you've learned.




Sorry about that. I'm so absentminded, I forgot I said I was going to post some more information on this process. 

I went on Ebay and ordered everything I need (I hope) to make the electrolysis unit in the diagram a couple of posts back. Two items showed up in the mail today and a third is still coming. The one still coming is an $18 (free shipping) rectangular graphite block (cathode) from Israel. The items that showed up today are an 8" piece of .5" titanium pipe from Latvia for the anode ($8 - $7 shipping) and a 12 volt battery charger from China ($16 - free shipping) that is supposed to put out 12 volts (14.4 volts) but requires 220 VAC at 50 cycles and only registered 7.2 volts DC when I plugged it in to 110 VAC 60 cycle. The stirring part will be the most difficult to make. I think I will just try stirring it by hand at first to see if I get results. A guy could rig up a sheetrock mud mixing paddle on a variable speed drill and mount it on a wooden frame over the cell. Only problem is, the paddle will have to be coated in epoxy to keep the aluminum or steel (even stainless) away from the chlorine solution. I was thinking even a perforated hose in the bottom hooked up to compressed air might keep everything stirred up.

The most interesting thing to see is what will happen to the gold at the cathode. Will it stick to the graphite cathode and plate it or will it fall below the cathode? Some people think it would be a bad thing to have it stick to the cathode but I don't know, at least it would be separated from the sand and mud and, once its only gold and graphite, I could always just scrape the gold off the cathode. Any graphite stuck to the gold would probably burn off during the melt (I hope). 

Tonight, I PROMISE I will sit down and explain everything that is going on in this cell. It is more complicated than it looks, although still very safe, and it has just about driven me nuts trying to understand it.


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## Traveller11

Okay, late again but here goes.

The electrolysis of brine (saturated salt water) will, below 50° Celsius, produce sodium hypochlorite (bleach) NaClO. Above 50° Celsius, this electrolysis will produce sodium chlorate (NaClO3).

If the pH of the brine is 7 at the beginning of the electrolysis, it will slowly climb to 8-9 with the production of hypochlorite/chlorate. There is a reason for this. During electrolysis, chlorine gas (Cl2) will deposit at the anode (+) and sodium hydroxide (NaOH) will form at the cathode (-). These will only exist briefly before combining to make hypochlorite (NaClO) and hydrogen (H2), releasing H2 to the atmosphere. HOWEVER, this process is far from perfect, and a minute amount of Cl2 will not combine with the NaOH from the cathode. This Cl2, as it is being produced in molecular form, will easily dissolve in water, giving us two compounds: hypochlorous acid (HClO) and hydrochloric acid (HCl). As hypochlorous acid (HClO) is a very weak acid, it will not do much to lower the pH; not nearly as much as the HCl. But, as there is an equal amount of NaOH forming at the cathode as there is HCl and HClO at the anode, it is obvious that there is more base being formed than there is acid and this will cause the solution pH to rise. HCl and NaOH will neutralize each other and become NaCl and H2O.

Now, as to why pH is so important. Sodium hypochlorite bleach (Clorox) has a pH of over 12, due to NaOH added as a preservative. NaClO at pH +12, is a very stable compound and, for this reason, is a poor oxidizer (disinfectant). Look at this graph for a few moments:




OCl is the sodium hypochlorite molecule and HOCl is the hypochlorous acid molecule (HOCl = HClO). As can be seen, lowering the pH of Clorox below 12 will begin to convert some of the NaOCl to HOCl. At pH 7.5, there will exist a 50/50 mixture of hypochlorite/hypochlorous acid. Lowering the pH to 5 or less will begin to cause Cl2 gas to be released. We want HClO, as it is a powerful oxidizer that will put gold into solution as a chloride. BUT, we do not want this solution to become acidic (especially below 5, as the bonds of oxides such as black sand will be broken and iron will go into solution as a chloride) and it is desirable to keep the pH between 7-8. It must be understood that, even with the 50/50 split between hypochlorite (stable) and hypochlorous acid (oxidizer), it is still possible to use up almost 100% of the chlorine as oxidizer. This is because as soon as you consume some of the HClO as oxidizer, some of the NaClO will instantly convert to HClO to maintain the split mandated by whatever pH the solution is at. Think of the hypochlorite as the reserve, and the hypochlorous acid as the workhorse. If the solution pH is 7.5 (see graph) this shift will constantly replace used up HClO until there is virtually no hypochlorite left and still maintain the 50/50 split.

More tonight.


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## tcpoint

Traveller11,

Did you get all the parts from ebay and have a chance to rig something up? Hope you had good results. Curious about how your experiment is coming along.


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## niteliteone

tcpoint said:


> Traveller11,
> 
> Did you get all the parts from ebay and have a chance to rig something up? Hope you had good results. Curious about how your experiment is coming along.


I too, am following with interest. I hope all is going as planned, as I have some black sands that are looking for a better way to get cleaned of values.


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## Traveller11

Note: HOCl and HClO, plus NaClO and NaOCl are the same formulas, just written differently.

Okay, I got all of the parts from Ebay; the graphite bar from Israel, the titanium pipe from Latvia and the battery charger from China. I have given up on the Chinese battery charger and purchased a good 6/12 volt, variable amperage battery charger from Walmart. I have also decided not to use the titanium pipe as an anode, on the advice of another member, as it turns out that, if the titanium is not platinized, it requires an immense amount of current to use it in electrolysis. What I did was saw the graphite bar in two lengthwise, making two electrodes.

I also found out that modern battery chargers require a battery to be hooked to them before they will begin charging. To facilitate this, I drilled 1/4" holes in the top of each electrode, crimped eye connectors on to the end of two pieces of 12 gauge wire, and connected these to the electrodes with 1/4" stainless steel nuts, bolts and washers. On the other end of the wires, I connected the two alligator clamps salvaged from the Chinese battery charger.

With the battery charger connected to a 12 volt battery and the anode and cathode immersed in an ice cream bucket half filled with heavily salted water and liquefied clay that hopefully contains fine gold, and the alligator clamps from the electrodes connected to the battery terminals, I started the charger on 12 volts at 2 amperes.
Predictably, a large amount of bubbles began surfacing around the negative cathode. A little later, a much smaller number of bubbles were noticeable at the positive anode, and this was to be expected, as well. The bubbles at the cathode (-) are hydrogen, and as they were in the majority, they are proof that the cell is working at an appreciable efficiency and doing the following:

NaCl + H2O + e = NaClO + H2 (NaClO being sodium hypochlorite or bleach)

As the pH of the solution was still likely below 8, about half of the NaClO would instantly convert to the powerful oxidizer hypochlorous acid (HClO) which is, along with NaCl, what we need to put gold into solution as AuCl3.

The much smaller numbers of bubbles rising at the anode (+) were chlorine gas (Cl2) and their existence is proof of the inherent imperfection of this process, small as it is. When the electrolysis of the brine solution first dissociates everything, different components are attracted to the anode and different components to the cathode. Sodium, oxygen and hydrogen are attracted to the cathode and form the strong base sodium hydroxide (NaOH). Chlorine gas is attracted to the anode. In a perfect world, these exist only for a fraction of a second before re-combining to make NaClO (bleach) and H2. When this does not happen, we begin to get a buildup of sodium hydroxide (NaOH) in our solution and, as it is a base, it begins to make the pH rise.

The rising pH should be countered by the chlorine gas (Cl2) at the anode but is not for two reasons. As Cl2 gas evolves, most will dissolve in the surrounding water, giving us the following reaction:

Cl2 + H2O = HCl + HOCl (hydrochloric acid and hypochlorous acid)

The hydrochloric acid (HCl) is a very strong acid and counters the base NaOH in the following formula:

HCl + NaOH = NaCl + H2O (interestingly, right back where we started)

However, the hypochlorous acid (HClO), although a powerful oxidizer, is a very weak acid, and does little to affect the pH of the solution. Making matters worse, the Cl2 lost to the atmosphere does not make any acid and, with the predominance of the NaOH, the pH of the solution will ultimately rise to between 9-10. I think the addition of the stirring paddle shown in the diagram would help here. If the solution is not moving, it would not take long before the water around the anode was saturated with evolving Cl2 and unable to accept more. If the water were moving, there would always be fresh unsaturated water around the anode ready to dissolve Cl2 and diminish the amount of Cl2 escaping to the atmosphere.

Another reason for the constant stirring of the ore, so I am told, has to do with silver chloride (AgCl). Most gold contains some silver and it reacts in this process as well, making AgCl. While stirring the ore will keep it well exposed to our solution, it turns out that AgCl, being an insoluble chloride, tends to deposit a coating on everything in the ore. When this coating covers a particle of gold, it prevents it from contacting the solution. As it is not adhered very strongly, constant movement of the ore and the abrasive action of other particles easily knocks the AgCl from the gold particles.

As this process requires the NaClO to be in its lower pH alter ego state of HClO in order to oxidize gold (see HClO/NaClO chart a few posts back), and the optimum pH seems to be from 7-8 in order to keep about a 50/50 mixture of NaClO/HClO, it is necessary for us to artificially lower the pH as it begins to rise. To do this, we need a good pH tester (one decimal) to monitor the pH of the solution. If it does rise above 8, minute additions of HCl or even acetic acid (vinegar) are enough to bring it back to the desired level, closer to neutral. One important thing, we do not want this solution to become acidic, and a pH of 6 is about as far as we dare stray. Any lower, and two things occur. At a pH of 5, our solution will begin to give up great amounts of chlorine gas (Cl2). It will also be acidic enough to break the oxygen/base metal bonds of any oxides in our ore. In particular, the acidic solution will begin to break up the oxides hematite and magnetite, in our black sands, and the liberated iron will immediately go into solution INSTEAD of gold. This last part cannot be stated strongly enough.

The big question still remains, will the gold, once liberated at the cathode, merely fall to the bottom below the cathode, or will it plate out and adhere to the graphite cathode? I have had it suggested that both will happen but, of course, only one is possible. To this end, I have written to a graduate student at UBC who, along with his professor, was involved in an artisanal miners program dedicated to eradicating mercury from Third World artisanal mining operations. This electrolytic process was part of that program, and I believe one or both of them actually saw a prototype in action, and might be able to tell us where the gold ends up. Believe it or not, this electrolytic process was originally designed to recover mercury from placer mining tailings. While it worked exceptionally well at recovering mercury, the tailings, unbeknownst to the operators, also contained a great amount of ultra fine gold that the mercury had been unable to amalgamate with, and this electrolysis process also recovered 95% of that gold. Another question I have is, if the AuCl3 is broken up at the cathode, liberating Cl2 to make more HClO, and the gold does NOT adhere to the cathode, what stops the liberated gold from simply re-reacting with more HClO to make yet more AuCl3?

One thing for sure, I am not only making chlorine gas; I am also making bleach. Shortly after turning the current on, I moved the anode and ended up sticking my fingers into the solution. Because of the almost neutral pH, there was no stinging or burning but I could definitely smell Clorox on my fingers.

I think the next step is to construct a proper bracket to hold the electrodes, followed by some sort of stirring mechanism to keep the ore and solution in motion. As I said before, any stirring mechanism in contact with the solution either must be made from plastic or, if made from steel or aluminum, coated with plastic to keep these base metals out of contact with the chlorine solution. Even stainless steel is not immune to chlorine. The only affordable metal one could use would be titanium, and I suppose a paddle made from titanium pipe and blades could be fashioned; either fastened together with titanium screws or bolts or welded with titanium welding rod (is there such a thing?). Another thing to do is to begin monitoring the solution pH to begin to get an idea of how often it is necessary to intervene and lower the pH.

It may be necessary to build an isolation chamber for the cathode employing anion exchange membranes, if it turns out the gold does not plate onto the cathode. These membranes would allow the passage of AuCl3, Cl2 and NaOH but prevent gold and ore from re-mixing. Once again, AgCl coating the membranes could become a problem.

Slow process but, hopefully there is progress being made here.

Bye for now.


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## maximumpat69

long time lurker here, much respect to the ladies and gentlemen of the forum are due first. looking forward to more on this!


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## Traveller11

I received an email back from my friend at UBC and it brings up some interesting points. Here it is:

"Bob,


Good to hear from you and even better to hear that you are still working on this and that your property is better that you thought. 

I must say your email was a wonderful read. For starters it seems that your science and understanding is spot on. As for where the gold ends up (at least from my trials) the short answer is that it ended up in both the solution and on the cathode.

But the longer answer is more interesting.

I've attached a picture of the setup I was using while trying to get proof of concept for research funding. The 'hotplate' is only a magnetic stirrer. The anode and cathode are simple rectangle graphite electrodes - nothing special. As you can see, the slurry just stirs about, and in my case it was pretty vigorous. This means that any deposition onto the cathode had to contend with this abrasive factor.





Overall gold dissolution was very high (>75). As measured by tails. Gold did remain in the clear/pregnant solution and was about 50% of the overall Au dissolution, meaning that the rest was on the cathode. Unfortunately I was not able to optimize the transfer of Au onto the cathode or figure out what was causing the Au to stay in solution and not on the cathode. I would guess that slowing the very turbulent flow I had at the cathode (by whatever means necessary) would be a good first step. But like you said, you'll have to keep in mind the ion-exchange rate through whatever barrier you have and in a direct slurry that can be challenging. With that in mind, I don think the practical answer lies with anionic barriers while using a slurry. I do know that cathode shape design is key to this, but never got into that aspect of things. My first guess however was a riffled cathode that allowed for areas where the solution could slow down... think the surface of a golf ball or something wafers.



Gold was indeed plated to the cathode and at a grade 2-3 times that of the ore in a sludge like layer about 1/10th the thickness of the cathode itself. Once done, I simply pulverized the loaded cathode and sent it to assay. For a large version you could directly smelt the Au-cathode in this manner too. Keep in mind that although I was not able to recover all the Au directly onto the cathode, filtering the solids out of the final pregnant leach and then using a recovery method like Merrill-Crowe (Zinc shavings and the pregnant leach under vacuum) could be an easy way to recovery what was not picked up by the cathode. You'd have to test the reactivity of Zn with a pregnant leach, but that would be pretty easy to test out.



I would also encourage you to took at other halides in combination with salt. For example, Bromine gold chemistry is also known within gold extraction but finding research on combination halide electrolysis is pretty rare. Combinations of two halides in a electrolytic leach could help each other in acting as intermediary steps in gold dissolution or in maintaining Au in solution. It's something worth trying out in tests should you ever get a working prototype. Given what you were able to find out on your own, you may stumble across papers/info on these ideas. If you do, I would love to have a copy of whatever you find.



Let me know if that answers your questions and keep them coming!



Cheers,

Adrian"

------------------------------------------------------------------------------------------------------------------------------------

Wow, I had heard of magnetic stirrers before but had no idea what they were. What a simple but amazing concept! With any luck, the stirrer could be scaled up somewhat for a larger container.

I wrote back and asked him if the "clear/pregnant solution" was "clear" as in a glass of water or whether it was a "clear" golden brown solution (auric chloride). I am still not sure if the gold goes into solution as auric chloride (AuCl3, Au2Cl6) or terachloroaurate (AuCl4) and what effect this has on the appearance of gold in solution.


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## Traveller11

I got to thinking about the use of a magnetic stirrer and it occurred to me this could present a small problem; one often encountered by placer miners attempting to separate fine gold and black sand.

As the magnetite portion of black sand is highly magnetic, it will be attracted to the magnetic components of the magnetic stirrer. This would be okay, if it were not for the fact that magnetite particles being attracted by a magnet have a tendency to bulldoze fine gold particles ahead of them. These get trapped on the magnet and often rob the miner of gold as the fine particles will end up in the tailings. 

However, as the magnetic stirrer will be keeping the chlorine solution and the rest of the ore in motion, it may be that the trapped gold particles will still be exposed to the chlorine solution. If not, a plastic or epoxy coated metal stir paddle connected to a motor should keep things stirred. I was also thinking of adding, at the bottom of the tank, a plastic perforated air line. By feeding compressed air through this and aiming the perforations downward, the bottom of the tank would be scoured and all of the ore and chlorine solution would be kept in motion.


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## butcher

Traveller11,
I sure do enjoy reading your posts, and your work in this area. 
Thanks


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## shaftsinkerawc

Supposed to be some of the REE are magnetic. Should save all your black sands to be sold or reprocessed.


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## Gratilla

Hi T, a few thoughts on your last 2 msgs.

Agitation: I don't think vigorous agitation (with magnetic/mechanical impellor or bubbles) is necessary. Slow turning of a drum (even manually) should sufficiently expose all ore surfaces to the electrolyte (at less cost and equipment).

Abrasion: If abrasion of the cathode is a possible concern, then perhaps a cell (separate from the ore) is the way to go. I think the Shor System uses something like this. Take a look also at the Efftech thread at:

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=84&t=18399

In addition to mentioning a "divided cell" and "strict pH control", it also claims to (very) effectively strip solutions of dissolved metal ions - a point that you mention is of concern in one of your msgs above.

Also note the downloadable pdf's, particularly the technical one.


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## Traveller11

Gratilla said:


> Hi T, a few thoughts on your last 2 msgs.
> 
> Agitation: I don't think vigorous agitation (with magnetic/mechanical impellor or bubbles) is necessary. Slow turning of a drum (even manually) should sufficiently expose all ore surfaces to the electrolyte (at less cost and equipment).
> 
> Abrasion: If abrasion of the cathode is a possible concern, then perhaps a cell (separate from the ore) is the way to go. I think the Shor System uses something like this. Take a look also at the Efftech thread at:
> 
> http://goldrefiningforum.com/phpBB3/viewtopic.php?f=84&t=18399
> 
> In addition to mentioning a "divided cell" and "strict pH control", it also claims to (very) effectively strip solutions of dissolved metal ions - a point that you mention is of concern in one of your msgs above.
> 
> Also note the downloadable pdf's, particularly the technical one.



Hi Gratilla

This is one of the enigmas of this setup. As there is such limited information available on it, it is difficult to determine if the agitation is necessary to expose all of the ore to the electrolyte, or to assure that chlorine gas from the anode and sodium hydroxide from the cathode are adequately mixed to produce the hypochlorite and chlorates or if the agitation is necessary mainly to abrade the buildup of silver chloride on particles of gold that would prevent the chlorine from contacting said gold particle. I have seen all three points argued well.

Also, the logistics of installing an anode and cathode in a revolving drum may be somewhat insurmountable, although I am open to suggestions if you happen to have a design in mind.


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## Traveller11

Interesting article on the Efftech system. I wonder how ell it could be applied to a situation where the main feed has high levels of black sands (iron oxides), considering that, from one of their diagrams, there appears to be a cell filled with hydrochloric acid.

I think I will write to them to obtain their opinion on the matter. I will share with the forum any information I obtain.


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## Gratilla

The tried, tested (and simple) method of transferring electrical charge to rotating systems is with a couple of (spring-loaded) graphite bushes; take a look inside an electric drill or angle grinder for an example. Having said that though, the large circular cyanidation tanks in this area all use impellors.

I wasn't suggesting that the Efftech system was your solution, but that:
a) It confirmed one or two of your findings ie strict pH control (different electrolyte, different pH), and
b) It claimed solutions to open "problems" you are still looking at ie electrolyte scrubbing. Even if you might not have access to (proprietary) details, the fact that there are solutions is of great help, IMO. The (high surface area) carbon mesh/foam/fabric cathode also looks interesting. Doesn't one of our Mods offer this stuff on his website?


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## bmgold2

Check out Action Mining's System III leaching unit for ideas. Sounds like what you are building.

Here's a PDF with their instructions

http://www.actionmining.com/systemIII.PDF

bmgold2


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## SMY_Met

Hello Traveller11,

I will be doing a Research on Alternative less toxic lixiviants than CN & Hg (used in Cyanidation and Amalgamation practices by small scale mines here in my country) and is considering to investigate Chloride/Hypochlorite solutions as it is readily available and cheaper than Iodine. I am very much lucky to come across this forum and able to get very interesting points to begin with my study. If the result of my study would be convincing enough, then I will be presenting this alternative method/technology to the small scale gold mines group for them to adopt the new process.
Overview of my project proposal would be using gold oxide ores and will be comparing three ways of leaching the gold 1.) Drum-roll (same technique with bottle roll) and 2.) Electrolytic cell (same with your cell but no agitator, instead will have nitrogen blowing at the bottom) 3.) Enclosed tank with agitator, a pressure relief valve and 2 passages for nitrogen blowing 1 at the top & 1 at the bottom


Have read some studies related and you might also want to go through and might add to your compilation of great ideas..the pourbaix diagrams are really helpful here..
http://www.sciencedirect.com/science/article/pii/S030175160600192X
http://www.minproc.pwr.wroc.pl/journal/pdf/ppmp49-1.61-70.pdf


best regards,  
SMY


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## Reno Chris

The problem with halogens is that even if less toxic than cyanide, they are toxic (Warfare using Chlorine is outlawed by the Geneva Convention), they are volatile, very corrosive to any pipe or tanks used in handling the solution and expensive to use. This why cyanide took over the industry when the process was fully developed. 
Most small scale miners use gravity based processes - shaker tables, wheels, sluices, blue bowls, etc. Unless you have sulfide ores, gravity will usually recover the majority of the gold, and the rest is just too expensive for small miners to go after.


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## Traveller11

Reno Chris said:


> The problem with halogens is that even if less toxic than cyanide, they are toxic (Warfare using Chlorine is outlawed by the Geneva Convention), they are volatile, very corrosive to any pipe or tanks used in handling the solution and expensive to use. This why cyanide took over the industry when the process was fully developed.
> Most small scale miners use gravity based processes - shaker tables, wheels, sluices, blue bowls, etc. Unless you have sulfide ores, gravity will usually recover the majority of the gold, and the rest is just too expensive for small miners to go after.



I don't believe you have read any part of this thread very carefully, or you would understand the reason I have been researching chlorine lixiviation methods from the 1890's. It is true that, at this period of time, chlorine solutions were made by first producing chlorine gas. However, this toxic gas was passed through water where it quickly dissolved; making hydrochloric and hypochlorous acid. Other methods at the time involved the electrolysis of brine, which produced a mixture of sodium hypochlorite (bleach) and sodium chlorate; an even more potent oxidizer than hypochlorite. It should be noted that none of the articles from the 1890's mention the need for making these solutions acidic.

While many on this forum subscribe exclusively to the chlorine method of first covering gold in HCl and then adding bleach (NaClO) until great clouds of chlorine gas are given off, this method is only useful to refiners and is totally useless to the miner wishing to extract fine gold from black sand. The reason for this is simple. The black sand, being mostly oxides of iron, is completely impervious to chlorine until the pH of the solution drops below 4-5; at which point chlorine gas comes out of solution. Below this pH, the acidity of the solution begins to break the bonds of the oxides and iron goes into solution, instead of gold. This is why the old timers roasted their ground ores in the presence of oxygen. It was not simply for the sake of making sulphide ores release their gold, it was also to oxidize base metals in the ore to make them impervious to lixiviation.

Suffice it to say, leaching with chlorine solution at a pH of 7-8, at which pH it exists as a mixture of hypochlorite/hypochlorous acid, is likely the safest method of dissolving gold. The only dangerous part of the process is taking bleach, normally at a pH of 12.2+, and gently adding an acid to it to lower its pH to between 7 and 8. Using hydrochloric acid, this is a rather delicate procedure with occasional violent reactions and a potential for adding too much acid. For this reason, a good pH tester is recommended, along with adding acetic acid (vinegar) instead of HCl. Acetic acid is a far milder acid that produces no reaction and allows far more flexibility.

As far as being expensive, what could be less expensive to the small miner than a process that uses Clorox bleach (or calcium hypochlorite pool sanitizer), un-iodized salt and vinegar as its components?


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## Gratilla

Hi T, I had been considering bumping this thread to see what the latest is/was. I believe that you're very close to a successful system; what would be very useful though would be a brief overview/summary of all the msgs, links and pdf's pulling together the good stuff and filtering out all the dead ends. I had intended to do this myself, but you know what they say about good intentions and the road to hell. <g>

I was wondering whether a bump of the SALTEM guys might also be useful. It's been some time now since you last corresponded with them and they might have (or know of) a successful operational system. I'd volunteer to write (in exchange for an email address), if you like.


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## Reno Chris

> I don't believe you have read any part of this thread very carefully, or you would understand the reason I have been researching chlorine lixiviation methods from the 1890's.



Actually you are not the only person to post in this thread, and I was responding principally to the person who posted just before I did. However, I will say to you that the use of chlorine to dissolve gold from black sands is not the best way to treat black sands. You will note that the papers you quote are about treating hard rock gold ores - not black sands. As I noted in my post, for most small miners the materials they recover are best treated using "*gravity based processes - shaker tables, wheels, sluices, blue bowls, etc. Unless you have sulfide ores, gravity will usually recover the majority of the gold, and the rest is just too expensive for small miners to go after.*"

Its hard to convince folks of this, but there is nothing mysterious or magical about "Black Sands" most examples - like 99% - have only tiny traces of gold after proper removal of all the gold that can be recovered by gravity methods. Get assays done by a competent, qualified lab if you really believe your black sand holds unusual values. Get a fire assay done or have the test done by AA - use standard, well accepted methods. If the test shows just a trace or below detection - that's what you have. Almost nothing. Most back sands that do have gold, have free gold that can be best recovered with gravity based methods. Meaning it is best processed with jigs, vibrating tables, blue bowls, spiral wheels and the like. 

I am not trying to give you a hard time - I am a mining engineer with many decades of experience and I have processed many thousands of tons of ore with cyanide and processed many tons of black sand. What I am telling you is not some stuff I made up off the cuff, but what competent gold miners have determined from many, many years of experience.


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## oro-del-sur

Gentlemen, this is a terrific subject, very relevant. Excellent work!! In particular my congratulations to Traveller11 for starting the conversation and to James122964 for sharing his hands on method. A modern version of what once was the primary method world wide to leach gold from whole ores prior to the discovery of the cyanide method is now once again relevant but as an alternative to cyanide. How ironic. The beauty being that the chlorine process can also be engineered to minimize / eliminate the hazards of toxic off gassing and resolve inherent issues with iron and base metal compounds in natural ores. To a small/medium scale miner this is nothing short of a breakthrough. Even more interesting is the method that employs a chlorine generator (salt cell) and simultaneously collects the values. How cool is that? 

It's exciting to see the stage being set on this open forum which appears to be on the verge of developing/adapting the process for public interest…for the first time in history? The early processes in the late 1800's were all proprietary - the modern versions (iGoli and CETEM) also proprietary. This is an amazing space, thank you all! 

A few months ago (March) member Gratilla asks Traveller11 if he could summarize his works up to this point. I was wondering the same even if only some starting reference points, for those that want to follow along with their own testing and share the results with the group. I have been working with SSN but iron and base metals are an issue. It is a good aggressive leach but you can't even test the ORP without ruining your meter :-( 

Searching the forum turned up a few related topics which I am still reading through - much of it is working out the chemistry. I have complied the links and if anyone is interested I can post them. 

Thinking ahead a bit…a medium scale production vessel for concentrates: from what I deduce there is a need for slight agitation / stirring in a sealed vessel. Excessive pressure and heat don't seem to be problematic issues, so a simple rubber lined steel drum rotating on a horizontal axis (use 3M 500 or 5400 series adhesive for rubber -steel bond). Natural rubber is much more abrasion resistant than plastic and for the most part is chemical resistant. The drum could be scaled to any size. Side plates could be rubber lined to create a seal and bolted, removable for maintenance - sealed ports/hatches for filling and draining….maybe a small liquid sampling port? The drum can be belt driven - single or multiple belts wrapped around the drum / reducer-electric motor below with tension adjuster - or gear/shaft driven casters. Experimenting with the drum speed might achieve sufficient mixing and minor abrasion but additional "folding action" could be easily achieved with rubber strips (lifters) bonded to the liner. Actual paddles may not be necessary but if so, easily done (think cement mixer) by bonding in some type of poly plastic material with supports. I assume the idea is basically to keep the slurry in motion and prevent settling. For concentrates with bonded values you could eliminate the lifters/paddles and instead add some river gravel and larger round river rock to enhance abrasion and further reduce (grind) bonded particles for additional liberation of Au particles (would require a heavier duty liner, maybe material used for conveyor belts?) Essentially this is very much like a rubber lined ball mill but acting as a mixer and light grinding / abrasion. Dual function - grind and leach. You wouldn't run it as fast as a ball mill, just fast enough to churn the rock and gravel. 

Thanks again for hosting this forum and this topic. I have bookmarked this thread along with other related threads. Other than bookmarking the topic is there an auto-notification function that sends an email when threads are updated? I didn't see it in the user control panel. 

Jeff


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## FrugalRefiner

oro-del-sur said:


> I have bookmarked this thread along with other related threads. Other than bookmarking the topic is there an auto-notification function that sends an email when threads are updated? I didn't see it in the user control panel.


Unfortunately, the email notification does not work right now. You'll just have to check back on the thread from time to time.

Dave


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## Gratilla

Oro, thanks for the interesting post. I came across a pdf a couple of weeks ago that I think would be of interest to members following this topic. Titled, "Chloride-Hypochlorite Oxidation and Leaching of Refractory Sulfide Gold Concentrate", it can be found at:

http://www.minproc.pwr.wroc.pl/journal/pdf/ppmp49-1.61-70.pdf

Note particularly the Pourbaix Diagram on page 3/63, showing the pH ranges for the dominant species of Sodium/Calcium Hypochlorite, specifically:

pH < 3.5 - chlorine (Cl2)
pH > 3.5 and < 7.5 - hypochlorous acid (HOCl)
pH > 7.5 - hypochlorite (OCl)

with hypochlorous acid being reported to being the most effective. (This is pretty much in line with Traveller's findings.) Interestingly this would keep the pH above 3.5 and minimize/eliminate Cl off-gassing.

From personal experience I can't stress enough the importance of keeping track of ORP/Eh. Many reported problems can be solved with a good Eh meter and a Pourbaix Diagram. I use a Hanna HI 98121 and haven't had a problem measuring Eh/pH of my SSN so far (touch wood), but I do have a replacement platinum probe on order just in case.


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## oro-del-sur

Gratilla - Thank you for that. I don't have a background in chemistry but am gradually wrapping my mind around the concepts. The link you sent (study) was very interesting. It does seem to verify what Traveller11 has been searching for…the holy grail perhaps? The working pH is in the range he proposed - and seems to answer the question as to which derivative of chlorine is doing the most work. Dissolution and 82% recovery of Au after 2 hours seems fast but then again their sample was -400 mesh Au particles (which is like talcum powder, not seen with the naked eye). Even more interesting was their conclusion that the sulfides are simultaneous oxidized with subsequent recovery of Au from solution (I think Traveller also suspect this). If this is true, this skips the need for prior roasting with heat. This is a big deal. And so then it would add a third function to the vessel design I have in mind (for concentrates): grind, leach and oxidize sulfides in a single vessel. Gives me goosebumps. I ask myself is this really possible? 

The trick will be to keep the solution within parameters over a several hour period as the pH and ORP fluctuate. Any thoughts on that?…a method average Joe miner can manage? If the pH is adjusted does the ORP pretty much take care of itself? Adjusting the pH also maintains adequate production of hypochlorous acid? Is it all about the pH? 

I just bought a new Hanna meter and quickly rinse it in water after dipping in the SSN, haven't had a problem yet. How much do the platinum probes cost? 

Thanks again!

Jeff


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## Gratilla

oro-del-sur said:


> If the pH is adjusted does the ORP pretty much take care of itself? ... Is it all about the pH?


I see you've been reading the SSN.pdf, but this is one assumption that Lashley definitely got WRONG. Eh changes pretty much independently of pH and usually more dramatically.

Some time ago I leached four ore samples (3 gold, 1 galena) with fresh SSN, keeping track of the Eh/pH at each step. What I found was that while pH changed only marginally (around pH 0), Eh dropped from around 870 mV to between 480 and 360 (most dramatically for the galena), as chemical reactions "consumed" various components of the ores. Now, most importantly, as gold needs an ORP of at least 800 mV to convert to AuCl3, the SSN was no longer able to dissolve the Au.

Also SSN and stannous chloride (to a lesser degree) "go off", so it's recommended you start with freshly made samples.

These are also the reasons why a number of members have had bad luck with Gold Test Kits based on SSN and stannous chloride. And why I believe:



Gratilla said:


> Many reported problems can be solved with a good Eh meter and a Pourbaix Diagram.


*IMPORTANT:
There are a number of different standards for measuring ORP, although only two (SHE: Standard Hydrogen Element and Ag/AgCl) are now widely used. (SHE is about 200 mV higher than Ag/AgCl.) Most depressingly, most authors just ASSume you know which one they're using!!!???!!! *The Hanna uses Ag/AgCl (and so do I.)



oro-del-sur said:


> Dissolution and 82% recovery of Au after 2 hours seems fast but ...


Lashley states that SSN reactivity (ie gold dissolution) DOUBLES for every 11-13oC increase in temperature. Think about that for a moment. If you're working at 25oC and increase that to 50oC then the speed of your reaction will increase by a factor of four! Increase temp to 75oC and the reaction increases by a factor of 16! etc.



oro-del-sur said:


> Even more interesting was their conclusion that the sulfides are simultaneous oxidized with subsequent recovery of Au from solution ...


Sulfide oxidation is an important feature of most/all of the halide/chloride leaching systems developed over the past decade or so by systems such as Intec, Nikko, Sumitomo, Outotec, etc. All operate at temps between 85 and 110oC.


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## oro-del-sur

Gratilla, yes, you picked up on that. Lashley said if you're not able to measure the ORP just to keep an eye on the Ph and assume the ORP stays within range. Yes, you are right, hot SSN is aggressive as hell - I had dissolution of -200 mesh particles in less than 30 minutes. I like the performance but didn't like the hassle of removing iron et al prior to leaching. The rest of the message I was referring to the Iranian study (Iran?) 

So you are a fan of SSN - also use Halides. For ore concentrates what is more practical / effective from your experience? Or are you a switch hitter, go back and forth?

That's an interesting detail you point out about measuring ORP - will make not of that. 

I was just checking the concentration of the solution / dosage the Iranians used for their study (optimum result), not sure I got it right - 400g of chemicals / 200 grams of solids / liter or water (2:1 chemicals / solids - 1 dm3 = 1 liter). So, to treat 25 gallons of concentrate requires 340 kilos of chemicals and 225 gallons of water? Wow! Did I get that right?? So, strictly a lab procedure, question being what part is useful in the field knowing the optimum dosage is not feasible?


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## oro-del-sur

…correction, should be "will make note of that"


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## james122964

Hi all, seems someone found some of my work, well, actually like most things with gold, it is based on modern use of old technology.

I can tell you that you want the hcl and bleach to be balanced based on expected gold content, the reason to do this and why I mix them separately is that when
the chlorine initially forms it is CL- not CL2, the single CL atom is what directly chlorinates the gold, if other free metals are there it will chlorinate them also, but since the materials are not in a solution when the chlorination takes place, very little, metal ion exchange takes place.

Sorry to not be around much and I will help anyone that sends me a email, but I am in the country as in boonies and only have signal when the stars align just right

jim


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## Kbob

Hi

I have some gold (fine) concentrate that has a lot of galena (60%) and some chalcocite (5%). Normal gold smelting of the material results in a product that has way too much lead. Is there a way of using hypochlorous acid (HOCl) to dissolve the gold and later precipitate with sodium metabisulphite. i assume the galena will not react much with the HOCl (since lead chloride is largely insoluble)

thank you

Kbob


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## Deano

Chloride leaching of your concentrate is a difficult undertaking at pH 7.

To maintain the precious metals in solution you will need to have 20% sodium chloride in the solution, this will also solubilise the lead as lead chloride in stable solution.

Oxidising sulfides with hypochlorous acid/ hypochlorite will consume large quantities of your oxidant, you will be shovelling hypochlorite in by the bucketfull.

Another problem area is that the pH will drop rapidly as the sulfides oxidise, maintaining pH 7 now becomes a difficult undertaking with frequent caustic additions.

This is not a system that you can run unattended for several hours and you will still have the real problem of having a toxic lead chloride solution at the end.

I recommend either using cyanide on fine milled cons or finding a smelter which will buy the cons from you for the precious metals value.


Deano


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## fishaholic5

After running rotating "pressurised" HCl/ Hypochlorite leaches on Ore in bottle rolls, buckets and barrels over a period of time I have a few thoughts.

Most of my leaches were between pH 3 and 5 measured at the completion of the leach during filtration. This will vary depending on the type of ore, some will give a higher pH
The vessels were never more than half full of ore, mostly around a third, enough water was used to just cover the milled ore and then the chemicals added and the vessel sealed. 

The leach vessel initially pressurises as chlorine gas is produced, then depressurizes as the chlorine goes into solution. I believe that the pressurisation of the vessels in the 1890's was to force as much chlorine back into solution as possible and offset the risk of vessel failure under negative pressure during the leach.

The salt produced in the reaction helps keep the gold in solution. If there isn't enough salt gold can start dropping from solution during filtering. 
Newberry and Vautin mention this as being from the formation of excess HCl, I think it has more to do with salt levels and the pressure change when the vessel is opened. I also believe its why they used relatively coarse filters that allowed the passage of the small gold particles as they dropped from solution.
It can be a little frustrating at times but can be overcome by trial and error.

Lower pH and higher pressure leaches work faster. Higher pH >4 leaches don't attack Sulfides and Iron as quickly, leach times on fine gold are relatively quick. Leach times can be as short as 30min and the longest leaches I run now are 4hrs depending on the ore type and gold content.
Gold will start to adsorb back onto any silica in the leached ore in longer leaches.

Quantities of Chlorine will be gassed off when the vessel is opened and during filtering as well as any other gases created during the leach. Take precautions.
There is always a risk of vessel failure in a system subject to rapid changes in pressure.

Open agitated or rotated leaches at a higher pH take longer but much less Chlorine gas is produced. The same issues with adsorption of gold onto Silica occur with longer leach times.
They are much more user friendly but material may need to be leached several times.

Cheers Wal


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## fishaholic5

I've been revisiting my old experiments. This is the "Purple Mud" mentioned in the Newberry Vautin process. 



As mentioned in my last post here it can start dropping from solution within hours or even minutes of a pressurised leach being opened.
The speed of filtration in the old processes was critical in allowing it to pass through the filters before the particle size got too big.

My experience is that it can be reverse gravity seperated then processed seperately while the rest of the ore residue is re leached or put back into solution in the next leach.

Cheers Wal


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## fishaholic5

further testing shows that it can be dissolved with a HCl solution then precipitated normally with Iron Sulfate or Sodium Metabisulfite

I'm assuming from the reactions at this stage that it drops as Gold Oxide

Cheers Wal


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## fishaholic5

This is the Solution obtained by dissolving 1kg of the purple mud with a HCl solution. 5L of solution obtained was diluted to 20L with water before precipitation



And the start of precipitation with Iron Sulfate



Cheers Wal


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## fishaholic5

Another note:
PGM rich ores will form HexaChloro PGM salts in a concentrated pressurised leach system.
Its better to leach these ores with a more dilute open leach at a near nuetral pH to help avoid this.

Cheers Wal


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## fishaholic5

The use of a leach solution charged with a mixture of Calcium Chloride and Sulfuric acid to create Chlorine, added water and then pressurised to around 60psi (4 atmospheres) may have created a leach solution that contains Nitrates, Chlorine and Sulfate that could extract all of the PGM's as well as Gold.


Cheers Wal


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