recovery of gold from ores with chlorine in 1898

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 The cylinder with its contents was revolved for two hours, then the charge was withdrawn and drained nearly dry by suction, the resultant liquid being slowly filtered through broken charcoal on which the chloride crystals were deposited, in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.

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.

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.

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.

Click to expand...

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

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?

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?

Click to expand...

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.

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.

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.

Click to expand...

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.

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:

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:

Click to expand...

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?

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

Platdigger said:

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

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

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.

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.

Click to expand...

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.

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

Platdigger said:

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

Click to expand...

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."

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

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?

Click to expand...

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.

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.

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.

Click to expand...

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!