# White Precipitate on Bottom



## Stoneman

I believe I messed up completely dissolving a batch of 14k gold filled wire in AR instead of inquarting first and then using AR on the settled gold remnants.

The AR I used was sodium nitrate in muriatic acid. The acid was yellow before adding and I received a good reaction when the wire was added.

After disolving the gold fill completely in the AR, the solution's color was dard brown, almost black. When I have used AR to dissolve previous batches of high karat gold the resulting solution was nut as deep brown, almost black color as when I used the AR on the 14 gold fill wire. I have verifided that bronze metal is the base metal under the 14k gold-fill sheet. 

I then double filtered the solution, added urea until it no longer fizzled, and then added sodium metabisulfite. Immediately, I started seeing a lot of white percipitate form and settle. After 24 hours, the solution had a heavy layer of white crystals on the bottom and no dark gold mud like previous batches of gold I have refined.

I took a small sample of the white crystals and melted it. It melted into what looks like copper and on an acid streak plate does not test as gold.

Can I salvage the batch and what steps can I take to do it.

A big thanks to anyone that can help me salvage the batch.

Stoneman


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## butcher

Stoneman,
Yes you should have avoided the trouble, by removing the base metals, before trying to dissolve the little bit of gold.

Test solutions with stannous chloride, if values cement on copper, if barren of values treat for waste disposal.

neutralize powders, with NaOH, using pH meter or test papers, (rinse out salt water), incinerate the powders, then treat for base metals, (if tin I would do a little deferent than no tin), boil in HCl, then dilute, let settle, decant liquid while hot, boil powders in water, lower heat, let settle, decant while hot, repeat till no color is removed, neutralize powders again, rinse, and incinerate again, this time you can use a hot 35% nitric to remove base metals, with settling and hot water rinsing, till clear, this should leave you the more valuable metal to process, depending on how much gold fill you had originally there may not be much powder left..

There are alternative methods.

But most important, more important than your gold here, read Hoke’s book, and avoid this kind of trouble.


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## Stoneman

Thank you for taking the time to reply Butcher. I won't make this mistake again.


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## Dr. Poe

When reducing with metabisulfite, the temperature of the solution must be maximum hot! Gold will precipitate, so will Tellurium. Selenium, Lead, mercury, silver. The gold, tellurium, and selenium comedown as metallic. The lead, mercury and silver precip as sulfites (white). If the solution is too cold, colloidal gold will permeate the off-white mass.
If nitric remains a trace in the solution, some gold will precipitate as the white AuCl (mono-valent) attached to hypo sulfate (real name-thiosulfate). AuCl precipitates white, then turns off white, then yellowish white to brown as 3 AuCl gives 2 Au + AuCl3. My advise is to redissolve the mass into hot aqua regia, the lead, silver and mercury will stay down. Remove any oxidizer with urea into your solution at 160f or higher. 
Re-precipitate the gold with hydroquinone. The tellurium and selenium will not come down. Neither any PGM's. Dr. Poe


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## Harold_V

Dr. Poe said:


> When reducing with metabisulfite, the temperature of the solution must be maximum hot!


That's an interesting comment. 

I am under the impression that it's the sulfur dioxide that is liberated from metabisulfite that precipitates gold. Please correct me if I'm wrong. 

Assuming I'm not wrong---and, considering I used SO2 as a precipitant for years on end, one thing I know to be true is that said precipitation is an exothermic reaction--and that it comes to a halt when heat becomes excessive. That occurs well below the boiling point of water. Can you please explain your position on this matter?



> Gold will precipitate, so will Tellurium. Selenium, Lead, mercury, silver.


Those of us who have refined for some time know that gold and silver, aside from minute traces, are never in solution with one another at the same time in acid. Silver will have precipitated as silver chloride, aside from minute traces, a phenomenon that is well documented. Is your reference to silver, in this case, to the minute traces?

Harold


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## Dr. Poe

If any silver chloride is on the bottom of your beaker; and if all the nitric and nitrous is then removed, silver chloride will dissolve into the chlorides. It is the presence of the nitric/nitrous that makes silver insoluble.
If the temperature of a SO2 drop is too high, the drop will occur the instant the temperature starts to drop. All precipitations of gold must be done under very hot conditions (exception for cyanide systems) or else the particle size will be too small for settling or filtering. It's very difficult to separate tellurium from gold. You can drop a single gram of gold from a 55 gallon drum of diluted gold chloride by adding a small amount of nitric acid free tellurium tetra-chloride and then introducing sulfur dioxide gas. In my 32 years, I've only found two ways that completely separate them. Dr. Poe


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## butcher

I have questions here, what do I not understand?

“If any silver chloride is on the bottom of your beaker; and if all the nitric and nitrous is then removed, silver chloride will dissolve into the chlorides. It is the presence of the nitric/nitrous that makes silver insoluble” Dr. Poe


This is very confusing to me,

AgCl silver chloride is insoluble in water, in HCl, in nitric, although it may be in form of milky looking liquid or white powder, it is insoluble. Silver chloride may not settle very fast fluffy and floating, but still insoluble.

What little bit that does remain in strong acids like concentrated HCl or Aqua Regia, as I understand this is,
It is not the normal AgCl silver chloride, but is actually AgCl2 (two chlorides) (only in strong acid solutions) and when diluted AgCl2 converts back into the insoluble AgCl.

I do not understand the comment that if we remove the nitric or nitrous acid that silver chloride would dissolve into the salt solution (chlorides)????

It is the presence of nitric or nitrous that makes silver insoluble????

Could you say this where a simple non chemist can understand?

Dr.Poe, Help me understand this, if any Joe smith had said what you said here I would say that was a big pile of horse-pucky, but since you said this I feel I must either not understand what your saying or need more study of the chemistry involved here.


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## samuel-a

Harold_V said:


> I am under the impression that it's the sulfur dioxide that is liberated from metabisulfite that precipitates gold. Please correct me if I'm wrong.



As far as i know:

4 HAuCl4 + 3 Na2S2O5 + 9 H2O = 4 Au + 6 H2SO4 + 6 NaCl + 10 HCl

Where SMB is in exess:

Na2S2O5 + 2 HCl = 2 SO2 + 2 NaCl + H2O


You probably have noticed that at first additions of SMB there's no smell at all... it's only when things warm up too much or when gold is depleted, that the choking SO2 smell appears.


I'm confused with some of Dr. Poe statement as well.
For one example, i always ppt gold while very cold or at room temp, but never noticed a white precipitate...
Maybe Au(I) does produced, but redissolved immediately by the HCl? Maybe more clarification is needed.


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## Dr. Poe

Not only does some silver chloride dissolve in acid (HCl), but also NaCl and just about any heavy concentration of the chloride ion. It's plain water and aqua regia where AgCl is least soluble. 
But there is something way more important to discuss than the solubility of small amounts of silver in strong solutions of nitrogen expelled ex-aqua regia: It's the danger of oxalic acid or it's salts! If one neglects to remove the silver chloride from the gold solution, then reduces the gold with oxalic or one of it's salts, a compound of silver oxalate is formed.
Left with the gold powder, it helps with coagulation, BUT! It explodes when an attempt is made to cupel or melt it!
The tiniest bit will at least cause your bead to jump out of the cupel into the furnace. A larger amount could kill or maim.
To elaborate further: When a sufficient amount of silver is alloyed or mixed with platinum, the two dissolve together in nitric acid. Platinum, which doesn't dissolve normally in nitric acid, combines with silver nitrate.
When aqua regia or salt, or just about any chloride is added to the acid, the opalescent silver chloroplatinite is formed and not the very insoluble silver chloride. This is one way that silver can end up in a solution the same time as gold.

If one happens upon a solution of gold, platinum and silver, I suggest that you add more aqua regia and heat strongly until the platinum gives up the chlorine-silver for nascent chlorine, allowing the silver chloride to precipitate. 

HAuCl4 made by dissolving gold oxide with strong HCl and HAgCl2 formed also by dissolving AgCl into strong HCl will mix successfully without precipitation in the absence of an oxidizing acid.

As far as an explanation for a sulfur dioxide smell, you use too much. The oxidizers are first reduced by the SO2, remaining nitrates, peroxides, tellurides, etc. Then the gold chloride. What is left in the solution is hydrogen sulfite, H2SO3 which decomposes into water and SO2 gas when heated.
They only way that I will believe you can efficiently precipitate gold in the cold (Or room temperature) is when the solution is heavily concentrated! Even then some is bound to precipitate colloidally. Dr. Poe


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## Harold_V

Dr. Poe said:


> They only way that I will believe you can efficiently precipitate gold in the cold (Or room temperature) is when the solution is heavily concentrated! Even then some is bound to precipitate colloidally. Dr. Poe


I strongly disagree, and I have years of experience precipitating gold from heavily concentrated solutions as my evidence. 
It was my routine to evaporate until roughly 18 troy ounces of gold was concentrated to a liter in volume. I would then add three liters of ice to the filtered concentrate prior to precipitation, using SO2 from a cylinder, with a glass tube inserted within ½" of the bottom of the Pyrex cylinder(s) I used to use for precipitation. 

My observations, and they were consistent: As the gold precipitated, the iced water quickly became hot. When the temperature exceeded a particular limit,* precipitation came to a screeching halt*. That point was well below boiling. By adding more ice, I could complete precipitation. That, to me, is more than enough evidence to suggest that what you're saying makes no sense. 

When the precipitation stopped (from temperature), the solution was commonly very near being barren. When ice was added, the remaining gold precipitated much finer than that which had come down previously. I attributed that to the level of concentration, Here is where we must draw a line as to what anyone would consider colloidal. My understanding is that colloidal gold is so finely divided that it appears purple. At no time did I experience any purple in my precipitation, aside form one negative experience where I tried oxalic acid and didn't apply it properly. In that case, heating was required, and I applied the oxalic to a cold solution. What little gold precipitated did so as colloidal gold. I had a light purple solution that failed to settle. 

On a few occasions, and they were very rare, gold that was being precipitated (from the concentrated solution I mentioned) came down in a crystalline form, distinctly recognizable as gold crystals. They were extremely dense- settling immediately. 

Aside from the last traces to precipitate, when additional ice was added, my second refining of gold ALWAYS came down such that it settled almost instantly, although not with the distinctive crystalline structure I mentioned. 

My experiences, (over a period of approximately 20 years) using SO2, do not agree with your comments in any way. Early in my refining experience, I used ferrous sulfate for precipitation. It was ALWAYS applied cold, and I never had any issues. 

I would suggest to you that your comments may be appropriate for the use of oxalic acid, but they do not reflect reality when using SO2. 

Harold


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## Geo

is there a way to generate SO2 gas with material on hand (SMB,common glassware,vinyl tubing) without adding SMB directly into solution? i would like to avoid the salt produced even though its a minor nuisance.even at the cost of extra material as long as i don't have to order a lab gas generator it would be worth it for me.


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## Dr. Poe

Harold; First of all, I believe that 18 oz of gold in 4 liters of solution IS considered concentrated. Secondly; colloidal gold is formed in a multiple of colors. Not just purple. I will post a picture of the various colors from transmitted light as well as from reflected light as soon as I learn how to post a picture here. Clicking on the Img doesn't seem to work for me. I need schooling in computer savvy. 31 years as geochemist research doctor, I've met very many veterans like yourself that groaned loudly when they realized that I was right and that they had been throwing away small amounts of gold for decades. If exothermic reactions get too hot, try slowing down. I can see adding ice to cool a hot reaction, but to precipitate in the cold, ridiculous. I really thought that you guys were participating in a joke on me. Ha Ha. I found by further probing into the forum (to my astonishment) that you guys were serious. I almost regret to show you what you obviously have seen thousands of times. The real bummer is that up to 58% of a troy ounce per gallon can be made colloidal, stable to one hundred years.
Oh, by the way, colloidal gold is unaffected by stannous chloride or any reduction agent. It can be brought down by boiling to 1/3 or less or co-precipitation with base metal hydroxides, aluminum tri-oxide (Al2O3) or shaken with activated charcoal.
Coagulation by anode DC current. If you are like most of the refiners that I knew, you have a 'catch barrel" where you toss your "spent solutions". My work as a research chemist for Trans-Ore Research was to assay, analyze and 'break' refractory ores from all over the world. These were ores that gold could be seen under microscope, yet resisted all efforts (except mine) to process. I excelled in solvent to solvent extraction. Which reminds me, you can shake alcohol with colloidal gold as well to bring it down. 
Now I am going to humble myself a little bit here: As a refiner of natural ores, I'm world class, yet as a refiner of scrap metals, you probably have more experience than me. The question is: Which is more difficult? Dr. Poe


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## butcher

Dr. Poe,

I have been thinking of our discussion on silver chloride, I feel it is like two guy's walking down to the river, see's a pile one man saying do not step in that horse pile, the other sayin no its not from a horse, that is a donkey pile, in reality it was left by a mule.

we talk of solubility there are degrees of solubility,or insoubility.
when we say something is soluble or insoluble we are talking of realatively not exact, like black and white can have gray areas.

I feel where I misunderstood your comment was with how much was soluble,and the form of the silver chloride, I think now we were both thinking the same thing just not using the same language, almost all of us here have not had the chemistry background you have, so we speak a different language.

so you must understand when you say that pile is blue, one of use may say no it is black in reality it may just be a mule pile.
most important thing is niether one of us steps in it.


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## Noxx

You guys don't understand each others...

It is true that Oxalic precipitations need to be hot!

However, Harold is talking about SO2 precipitation (from a gas tank). Since SO2 is very soluble at 0*C and poorly at 100*C, he needed to cool his reaction with ice.

The precipitation is exothermic.


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## Dr. Poe

Yes, I was referring to bi-sulfites. In my experience, oxidizers including gold chlorides, eat reducing agents like my dogs will eat steak tid bits thrown to them. When I have used SO2 gas (under the hood) it was under very low pressure. It (the HAuCl4) always was very hot and spinning vigorously. As soon as I could see the precipitation, I turned off the gas and let it spin for about twenty minutes, sometime longer or until the gold dropped completely. Shining a light on the still liquid revealed if I was completely successful or not (Tyndall effect). For the non-chemists, the Tyndall effect is similar to seeing dust in a beam of sun light. 
Noxx, you are the genius that put this fine forum together (Not sarcasm). Thank you for the graph. Can I copy it some how to add to my collection? How can I send that picture of nano-gold samples to the forum? Is there a post on the forum that teaches how to do these things? I tried "search" and I tried "Tutorials" to no avail. Help, I'm new to internet not geochemistry.
OH, and I'm sure that we all agree that no two doctors agree completely on everything. I'm growing very fond of this forum and don't want to offend anybody. I'm here to get that satisfaction of knowing that I helped someone escape poverty by use of knowledge. Is there any refiner or assayer that hasn't had a bead 'spit' or pop out of their cupel? Did my post on the problems 
and dangers of silver oxalate bring back any unpleasant memories? I've got a lot more to add when I get the hang of making posts. Dr. Poe


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## samuel-a

Here you go Dr. Poe


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## tek4g63

I am new to this forum but I have to say that this is one of the best dicussions I have come across yet. I can't wait to see the pictures Dr!


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## Dr. Poe

These are the more common colors of colloidal gold. Green exists, but is rare. These are "Sol's", not solutions and are derived from pure solutions. Base metal colors blend. Cuprous or cupric salts adjusted to alkaline will co-precipitate the gold down. Read my previous post about the others. Now you "Newbies" know why some refiners hate to throw away some 'spent solutions'. Those of the left are the same on the right There's only 4 vials total here.
Give your thanks to Samuel-a.
PS: Please take note of the white foam on the right---White mono-atomic yet non-ionic sol.

Dr. Poe


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## Dr. Poe

When red changes to blue, slow precipitation soon follows.
Dr. Poe


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## butcher

Dr. Poe,
Thanks for the pictures of those pretty solutions.

I want to say how much I enjoy the knowledge you bring to the forum, I really enjoy your posts, and learn things when I read them, I really do not think you offend anybody here, you do seem to speak a language that I have yet to learn, so please do not be offended when I ask you about something you say, I would like to learn from you, and please have patience with me, I would like to understand your language, it may take me a while I have a thick scull, and knowledge is slow to sink in.

Why is it chemist and doctors speak a strange tongue, and you cannot read what they write?


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## Geo

I've never experienced any solution of this color except the purple one second from the left.i described it here on the forum but no one could tell me what caused it.if i remember correctly i cleared the solution with hot ammonium hydroxide. does that sound right?i was trying to precipitate gold from AuCl solution.after heating and the addition of the ammonia the solution cleared and the gold dropped out of solution.


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## Dr. Poe

One can also precipitate a sol of gold by simply changing the pH to just the other side of 7. From acidic to just alkaline or from alkaline to just acidic. You can expect some base metal hydrated oxides on the alkaline side to co-precip, insol acid salts on the acid side. Mainly I want you guys to see these pics. I know some of you will groan. Hopefully, a lot of you will have catch basins that can be re-worked for gold sols. When I get some pics of the platinum group sol's, I will post them too.
It's feels good to be appreciated.
PS: GEO: Never use concentrated ammonium hydroxide or ammonia to a gold solution. There is an extreme danger of explosion. Never let a spent solution sit overnight with any ammonia salt. The Christmas ornament industry has recorded several deaths from this problem as well as formaldehyde and formic acid. They since then have used electrodeposition to glean all spent solutions. Saves lives and brings in a little bit more money.
I would sure like to discuss with someone the Christmas ornament business. Any of you guys in that business?
Dr. Poe


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## RGJohn

Dr. Poe said:


> .....I would sure like to discuss with someone the Christmas ornament business. Any of you guys in that business?
> Dr. Poe



I am not in the ornament business but I do know what they are. I would prefer to remain upon the topic of gold refining please.
------
Could you tell us please what is each of those vials of colored liquids with the corresponding colloidal gold discs? Are you saying that the colors of the solutions ( or 'sols', I believe you call them) are due to the size of the colloidal gold particles in them? What are the scale or dimensions of those gold discs? How do you determine the size of the gold particles in solution? 
Why are they incapable of being detected with stannous chloride? Do they somehow agglomerate into larger blobs, then turn blue and precipitate? 
I'm a trifle sluggish so please take a moment to detail a few specifics and please correct me where I have drawn incorrect inference. It's rather hard for me to follow your writing.
Thanks in advance.


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## Oz

RGJohn said:


> I am not in the ornament business but I do know what they are. I would prefer to remain upon the topic of gold refining please.


Silvering Christmas ornaments are on topic in my opinion as the process used is hazardous to the ill informed and is often practiced by the novice unintentionally when refining, even if ornaments are not the goal.

Just my personal opinion, not necessarily that of this forum.


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## butcher

Knowing the dangers involved, when we mix these solutions is very important.
Much of what we do is extremely close to making these volatile solutions. 

There are times when we actually form these solutions and then back out of them before putting them into the very dangerous state.

As Oz say’s there are some who come here and jump off the cliff without checking to see how high the cliff is, or just follow some instruction running blindly towards the cliff but not knowing where they are headed.

And some may not have a clue about how these solutions and metals can react with each other.

The chemistry is also very vast, and even the more informed person can get himself into trouble with something he is unaware of.

Knowledge is important, as it can keep us from making something unintentional, also letting us know when we are forming dangerous compounds, and how to make them safe again , or just plain stay away from them.

But then again this knowledge is a double edged sword, we sure would not want someone getting Ideas, of how to make these things, and hurt themselves or others with this knowledge or think they are a chemist and start making this stuff without understanding what they are doing.

We must consider all audience with any of our discussion.


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## Lou

Dr. Poe said:


> When reducing with metabisulfite, the temperature of the solution must be maximum hot! Gold will precipitate, so will Tellurium. Selenium, Lead, mercury, silver. The gold, tellurium, and selenium comedown as metallic. The lead, mercury and silver precip as sulfites (white). If the solution is too cold, colloidal gold will permeate the off-white mass.
> If nitric remains a trace in the solution, some gold will precipitate as the white AuCl (mono-valent) attached to hypo sulfate (real name-thiosulfate). AuCl precipitates white, then turns off white, then yellowish white to brown as 3 AuCl gives 2 Au + AuCl3. My advise is to redissolve the mass into hot aqua regia, the lead, silver and mercury will stay down. Remove any oxidizer with urea into your solution at 160f or higher.
> Re-precipitate the gold with hydroquinone. The tellurium and selenium will not come down. Neither any PGM's. Dr. Poe




Anyone wanting to use urea and claiming that AuCl will precipitate from hot solutions containing nitric acid, does not know what he/she is talking about. AuCl will form after AuCl3 disproportionates from one leaving HAuCl4 on the hot plate too long.

There's no thiosulfate, nor does mercury precipitate or even silver precipitate. I don't even know why you listed some of these elements--the original poster was talking about gold filled, which need not be inquarted anyway (there's enough base metal clad over to serve as an inquart..


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## Lou

Geo said:


> I've never experienced any solution of this color except the purple one second from the left.i described it here on the forum but no one could tell me what caused it.if i remember correctly i cleared the solution with hot ammonium hydroxide. does that sound right?i was trying to precipitate gold from AuCl solution.after heating and the addition of the ammonia the solution cleared and the gold dropped out of solution.



If you want, we can discuss why it forms and different ways gold nanoparticles are made. I've done them probably a half dozen ways, characterized them with UV-Vis, TEM, DLS, and other techniques beside. I really think they're fun!


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## Stoneman

I appreciate all the posts and careful thought invested by the forum members. The challenge is deciding the correct choice of remedial steps.
Based on all the responses. I'm not a chemist, nor have access to high tech lab equipment or chemicals.

Could someone read my original post and explain in simple steps what they would best recommend. Feel free to explain in detail what you would do. I have successfully refined several batches of high carat gold using aqua and percipitate, but made a mistake in not inquartating the large batch of gold fill before using aqua to dissolve only the gold. I will not make this mistake again.

The batch of gold fill, so this why I'm attempting to salvage it rather than writing the batch off as a mistake. The large amount of white percipitate surprised me. The only metals placed into the agua were 10/20 gold fill wire which is 2.6% gold by weight with the underlying base metal being bronze core. No silver or other precious metals. The batch was extremely clean with no junk metal from other sources and came from a reputable refiner. Only 10/20 gold fill wire. I'm a jeweler and the material was clean.

Thanks again to everyone for replying. I have learned much more than I knew previously and appreciate everyone's help.


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## Dr. Poe

I apologize to Lou for not using an indentation for another paragraph. I was referring to "Cold"
As a real chemist, I can tell you by experience that the presence of a trace oxidizer in a "cold" solution will change the nature of sodium metabisulfite. In a hot, agitated solution of gold acid, SMB instantly decomposes to release SO2 gas which doesn't dissolve into solution, but instantly reacts with the gold acid, tellurium, selenium or nitric. The SO2 doesn't make it to the surface until the reduction is done. With SO2 gas from a steel bottle (at 4 lbs pressure), one can see a bubble start to form at the end of the ceramic tube instantly turning dark and dispersing . Eventually all the gold is reduced and SO2 gas starts to bubble to the top. I turn off the gas then and just allow it to stir until the solution clears. When I'm using sodium metabisulfite, a spoon full at a time, into the spinning fluid, it instantly reacts and no smell of SO2 gas is detected. I do this under the fume hood as a standard safety procedure. Using my hand to grasp some air from above the mix (pulling it to my nose), when I detect SO2 gas, I stop adding SMB.
The only way my dog would miss a piece of steak thrown to him is if he has one already in his mouth.
He won't let the second piece leave his area (He's on a chain) even then. SO2 doesn't clog with gold on the surface, slowing down the reaction slightly as if a copper wire would do. It turns into gold dust and sulfuric acid. Once I turn the SO2 gas on or use SMB, the reduction takes place totally in only a few seconds, hindered only by the rate of gas flow. Remember the statements that I have made of this phenomena of mono-valent gold precipitating is only by cold working the solution.

About the Christmas tree ornaments, I only want to talk with a pro in the business and about the changes made in the last twenty years for safety reasons.
Dr. Poe


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## Dr. Poe

Stoneman said:


> I appreciate all the posts and careful thought invested by the forum members. The challenge is deciding the correct choice of remedial steps.
> Based on all the responses. I'm not a chemist, nor have access to high tech lab equipment or chemicals.
> 
> Could someone read my original post and explain in simple steps what they would best recommend. Feel free to explain in detail what you would do. I have successfully refined several batches of high carat gold using aqua and percipitate, but made a mistake in not inquartating the large batch of gold fill before using aqua to dissolve only the gold. I will not make this mistake again.
> 
> The batch of gold fill, so this why I'm attempting to salvage it rather than writing the batch off as a mistake. The large amount of white percipitate surprised me. The only metals placed into the agua were 10/20 gold fill wire which is 2.6% gold by weight with the underlying base metal being bronze core. No silver or other precious metals. The batch was extremely clean with no junk metal from other sources and came from a reputable refiner. Only 10/20 gold fill wire. I'm a jeweler and the material was clean.
> 
> Thanks again to everyone for replying. I have learned much more than I knew previously and appreciate everyone's help.



I apologize that our debate wandered from your needs. 

The key here might be that "Bronze is made from copper and tin. Nitric forms a white precipitate of tin oxide, insoluble in nitric, but soluble in aqua regia or muriatic acid (HCl). Now I'm not sure of my memory of just how insoluble tin oxide is in strong or week nitric acid. Does anybody have a better recollection of the tin oxide solubility in in strong nitric?
Never mind, I just checked my CRC handbook, alpha SnO2.xH2O is soluble, but not meta SnO2.xH2O (white)
Dr. Poe


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## Stoneman

Dr. Poe,

That could explain the white percipitate as compared to other batches of high karat gold I have refined in which no white percipitate formed. You may have suggested a remedy already, but could you explain the most simple process to correct the mistake I have made by not inquartating first. All the gold is still there. I have not disposed of anything including the white powder in the bottom of the solution.

Thanks again for your assistance. If the batch were not economically valuable, I would environmentally dispose of it and chauk it up as a simple lesson.


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## Lou

Stoneman,

What likely happened is that you added an excess in sulfite to the solution, which was very weak in gold concentration, since it was gold fill. This produced copper (I) chloride, a white-gray compound that isn't very soluble in sulfur dioxide-saturated water, even when acidic. The gold is probably entrained in that. 


If the material is gold fill, you'd be best served to melt it, corn-flake it, and then digest it in 15-20% nitric acid. Any higher a concentration, and you will form that gooey hydrous tin oxide (metastannic acid) that will impede filtration and the reaction. If that needs removed, use hydrochloric acid.



and Dr. Poe,


as a real chemist myself, I can tell you that it doesn't practically matter if you have a trace oxidizer present in the gold containing solution. Gold (III) is a very strong oxidant. It's absolutely fine to precipitate from a cold, concentrated solution. Harold noticed it heats up because of this redox reaction of gold (III) going to gold (0) and SO2 going to SO4-2. It's exothermic due to 1.) formation of stable nonreactive sulfate anion, and heat of ionization/speciation, 2.) formation of insoluble gold which removes itself permanently from the equilibrium, at least if no other oxidant remains in the system. 

I understand where you're coming from about wanting a hot solution. That's well and dandy for kinetics purposes, but this is primarily a thermodynamics-driven reaction. Hell, you can see the dichotomy quite easily if you leave excess nitric acid in your chloroauric acid solution while gassing with LSO2 from the cylinder. A good portion of the gold will drop as heavy blonde gold powder, and then nitrogen oxides will be expelled. This is due to 1.) the HCl and residual nitric acid making nitroysl chloride and dissolving the gold sponge and producing NOx (this is exacerbated by the heat of reaction of the reduction), and 2.) that the redox potential changes when the gold solution gets to a certain depleted concentration and higher temperature and the nitric acid ends up oxidizing the sulfite or sulfur dioxide rather than the gold. Any subsequent precipitate will be of lower quality than the initial "drop". The reduction is faster at higher temperatures, but also less efficient because of the greatly decreased solubility of the reductant, SO2, in the medium due to higher mean kinetic energy in the solution. So starting cold and letting it warm up is best practice. I should say that everyone should cold filter their chloroauric acid solutions before reduction. Preferably with a slight dilution with ice before hand to remove complexed AgCl (which, as Butcher noted above thread, is present in hyperchloridic milieu). 


If you'd like a better explanation of the reduction process and subsequent nucleation and ripening of the precipitate, I can direct you to some interesting highly theoretical reading that should answer all of your questions and help you better understand the nature of producing high quality gold (whether that be with sulfite, or any reducing agent). 

Also, if any Te or Se comes down with the gold, it's not due to the reducing agent. They're just tenacious with their liking for gold. A review of HSAB theory will help you appreciate why the affinity is so high, and of course you can find other more fundamental reasons when you look into the CFT of what's being produced. I routinely used thiols/mercaptans for modulating surface chemistry of gold nano particles. It's basically SOP because the other chalcogenides REEK TO HIGH HEAVEN. Pedantics aside, as any good geochemist knows, ALWAYS and CAREFULLY roast your cons! 

Nucleation theory is one of my interests, especially as it pertains to precious metals. You can tell much about what you have and how it'll melt and work based on the quality of the sponge.


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## Dr. Poe

Lou, you are a breath of fresh air. The only point that we disagree is in the redox potentials of gold acid and the AR.
Or really the redox potentials of gold acid and trace nitric in a chloride solution. Then again they are so close that concentration differences can change the electromotive forces. As to tellurium, 1.27 angstroms of tellurium to 1.38 for gold ion partially explains their partiality for each other. SO2 reduces tellurium salts to a zero charge. Tellurium is not likely to be present except from natural ores or from e-scrap. I don't know of anyone using it to brighten gold plating anymore. It used to be quite common. One of my problems is that I'm 60 years old now and a lot of things are in the "Used to be" category. 
Please everybody forgive me, it's entirely possible that I gave too much credit to the hot plate for the rise in temperature in my SO2 drops. I really didn't care about the solubility of SO2 in solution as I was counting on it's transformation as it made contact with hot gold acid. It looks like the "white precipitate" could be any or all from the low solubility of the mono-chlorides of silver, copper and gold or of the oxides of tin, tellurium. I think your theory of the production of cuprous chloride in situ merits my reflection.

There are some here at the forum that have stated that maybe I shouldn't reveal any chemistry of the production of Christmas tree ornaments. Do You agree? Is it too dangerous for this forum? 

Now that I'm no longer in a large modern laboratory, I'm looking for some used old fashioned equipment: A spectrograph like the ones used in high school chem labs in the nineteen fifties. A simple refractometer for checking the index of refraction to determine concentrations. I couldn't believe the price they asked for a small mass spectrometer. Just the hand held "pistol" type was nearing 60 thousand dollars.
Dr. Poe


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## goldsilverpro

http://www.ebay.com/sch/i.html?_nkw=bausch+and+lomb+spectrometer&_armrs=1&_from=&_ipg=


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## rusty

Dr. Poe said:


> There are some here at the forum that have stated that maybe I shouldn't reveal any chemistry of the production of Christmas tree ornaments. Do You agree? Is it too dangerous for this forum?
> Dr. Poe



Found this Russian site with a brief description on how ornaments are made, I was not aware that they silvered the inside of the glass orniment, Silver oxide, ammonia and distilled water in a certain proportion are injected into the decoration

I think it would be a very interesting topic.
http://englishrussia.com/2009/11/21/klavdievskaya-factory-of-christmas-tree-decorations/

Best Regards
rusty


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## qst42know

By the way they are dressed I'd say the building isn't heated.

I'll have to watch for some throw away bulbs to see how much can be recovered. 8)


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## freechemist

Dr. Poe wrote:

_When reducing with metabisulfite, the temperature of the solution must be maximum hot! Gold will precipitate, so will Tellurium. Selenium, Lead, mercury, silver. The gold, tellurium, and selenium comedown as metallic. The lead, mercury and silver precip as sulfites (white). If the solution is too cold, colloidal gold will permeate the off-white mass.
If nitric remains a trace in the solution, some gold will precipitate as the white AuCl (mono-valent) attached to hypo sulfate (real name-thiosulfate). AuCl precipitates white, then turns off white, then yellowish white to brown as 3 AuCl gives 2 Au + AuCl3. My advise is to redissolve the mass into hot aqua regia, the lead, silver and mercury will stay down. Remove any oxidizer with urea into your solution at 160f or higher. 
Re-precipitate the gold with hydroquinone. The tellurium and selenium will not come down. Neither any PGM's._

In case of 14k gold filled wire you don't have to worry about Tellurium (Te) Selenium (Se), Lead (Pb), mercury (Hg). These four elements can be of importance only in the first recovering steps for precious metals directly from their ores. Your 14k gold filled wire is a much farther processed material, and thus it is most impossible, that it contains even traces of these four elements.

Dr. Poe wrote:

_If any silver chloride is on the bottom of your beaker; and if all the nitric and nitrous is then removed, silver chloride will dissolve into the chlorides. It is the presence of the nitric/nitrous that makes silver insoluble._

Nitric acid and nitreous oxides (NOx; reduction products of nitric acid) have no influence on the solubility of silver chloride. It is only a high chloride concentration in solution, which will make AgCl a little bit more soluble in fairly concentrated HCl, in comparison to just plain water. This is due to the formation of a negatively charged anionic silver complex, AgCl2(-), which on dilution with water will decompose to AgCl and a chloride anion in solution.

Dr. Poe wrote:

_But there is something way more important to discuss than the solubility of small amounts of silver in strong solutions of nitrogen expelled ex-aqua regia: It's the danger of oxalic acid or it's salts! If one neglects to remove the silver chloride from the gold solution, then reduces the gold with oxalic or one of it's salts, a compound of silver oxalate is formed._

Don't worry about oxalic acid, too. The remnants of AgCl in solutions ready to precipitate gold out of them with oxalic acid are much too small, to be able to form silver oxalate. And more: silver oxalate is dissolved in strongly acid solution, contrary to silver chloride. And last, but not least: If not very pure gold (4x9 or better) has to be precipitated, SO2, sodium-sulfite and so on are preferred.

butcher wrote:

_Why is it chemist and doctors speak a strange tongue, and you cannot read what they write?_

Maybe, they don't try, thoughtlessly, forgetting that there are other people who would like to understand, too?
Maybe, they don't want others to understand?
Maybe, by longtime using "academic language" they slowly loose capability to use common language?.....
Whatever it is, don't forget, chemists and doctors are nothing special, they are human beings like you and me.

freechemist


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## Dr. Poe

:evil: Some gold plating is done with a trace of tellurium as a "brightener".
Silver chloride dissolved in strong HCl will precipitate immediately upon adding aqua regia or nitric acid.
The Conquistadors used salt (NaCl) copper sulfate and mercury in their arrastas. The Silver chloride (Horn silver) dissolved into the salt (NaCl), reacted with the copper sulfate, then was reduced and absorbed into the mercury.
Trace amounts of silver oxalate cause small explosions when heated, large amounts are deadly.
SO2 in the cold dissolves and saturates. Hot solutions of gold hydrogen tetrachloride need only contact SO2 to be reduced.
The SO2 need not be in solution to react with gold acid chloride. 
If insufficiently diluted, the SO3 formed robs the water from the reaction forming sulfuric acid and very much heat.
Hot, concentrated sulfuric swings the reaction back to the left. The biggest difference between what I have done and what
else was posted was in the concentration. Mine had water in excess of the water of crystallization. The sulfuric formed was not concentrated. 
I critiqued a book written by another doctor. The book was filled with mounds of good information and only one, fatal mistake: The Authors thought that chlorine could substitute for bromine in a cyanide leach for gold. Fatal mistake!
A reaction swings to the right when a factor is removed such as a gas or a precipitate. Chlorine forms cyano-chloride, which vaporizes at room temperature into the air and is a very, very poisonous gas requiring only one whisp to kill.
Bromine forms bromocyanide which must be heated far about room temperature to vaporize. 
Now I wonder if the instruction that you have received was incomplete.
Dr. Poe


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## freechemist

Dear Dr. Poe,

Thanks for your most elaborate reply on my post. For me it is full of information, but there remaines still one thing, I wish to be put in the right place. It concerns your wonder about my instructions. The answer is simple: what I have stated in my post is not based on working instructions I have received, but solely on my own experience and especially practice.

freechemist


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## butcher

Could someone read my original post and explain in simple steps what they would best recommend. Feel free to explain in detail what you would do. I have successfully refined several batches of high carat gold using aqua and precipitate, but made a mistake in not inquartating the large batch of gold fill before using aqua to dissolve only the gold. I will not make this mistake again.

I will help best I can, first you need to study Hoke’s book doing her experiments, and understand how metals are processed, to get fine gold.
Quartering would not be necessary with gold fill, but eliminating base metals is needed.
When gold percent is more than ¼ part in karat gold then in quartering is needed.

The batch of gold fill, so this why I'm attempting to salvage it rather than writing the batch off as a mistake. The large amount of white percipitate surprised me. The only metals placed into the agua were 10/20 gold fill wire which is 2.6% gold by weight with the underlying base metal being bronze core. No silver or other precious metals. The batch was extremely clean with no junk metal from other sources and came from a reputable refiner. Only 10/20 gold fill wire. I'm a jeweler and the material was clean.

You had too much base metals present, many of may be in your white salts, possibly: copper I chloride, lead chloride, silver chloride, table salt, other insolubles, and gold.
You may find you did not even have gold in solution, (use stannous chloride test to see), the base metals can cement gold out of solution.

Thanks again to everyone for replying. I have learned much more than I knew previously and appreciate everyone's help.

Hokes book you will learn what you need. 

Believe I messed up completely dissolving a batch of 14k gold filled wire in AR instead of inquarting first and then using AR on the settled gold remnants.

Eliminate base metals before putting gold into solution

The AR I used was sodium nitrate in muriatic acid. The acid was yellow before adding and I received a good reaction when the wire was added.

Base metals added with small amount of gold


After dissolving the gold fill completely in the AR, the solution's color was darn brown, almost black. When I have used AR to dissolve previous batches of high karat gold the resulting solution was nut as deep brown, almost black color as when I used the AR on the 14 gold fill wire. I have verified that bronze metal is the base metal under the 14k gold-fill sheet. 

Brown solution a good indicator of copper I chloride.


I then double filtered the solution, added urea until it no longer fizzled, and then added sodium metabisulfite. Immediately, I started seeing a lot of white precipitate form and settle. After 24 hours, the solution had a heavy layer of white crystals on the bottom and no dark gold mud like previous batches of gold I have refined.

Urea is only another contaminant in my opinion, and possible another ingredient in your white salt, SMB in excess is possibly another part of the white salt, depending on how successful the urea was at eliminating the excess nitric acid.
I would use evaporation process and throw that sack of urea on the grass where it may do some good, keep it out of your gold solutions.

I took a small sample of the white crystals and melted it. It melted into what looks like copper and on an acid streak plate does not test as gold.

It was copper and other salts of metals, If you had silver you probably would have lost it, it could still have some gold in it, I would not trust streak test here.

Can I salvage the batch and what steps can I take to do it.

If solutions test with stannous chloride, if values cement on copper (you could use the copper button you made), save the copper button you made and powders cemented if any, only treat and discard waste (properly) after testing to be sure they are barren of values.

A big thanks to anyone that can help me salvage the batch.

You have not lost no where near the values (in this batch) that you will be loosing if you do not follow these next instructions.
Forget about refining, concentrate on collecting values, and learning how to deal with all metals and how to recover and refine them, learn the safety of processing and dealing with waste, Read Hoke’s book do the chemical experiments with these metals and acids she suggests, learn to test metals in solution, learn the process and reasons she says how to do the processes, why she uses different processes for different materials. Study the forum read about many others who make the mistake your making now (jumping off a ship in the ocean without a life preserver yelling for help, not reading the manual, or listening to others, that may have told them to use the life boat).
Save yourself from any trouble you may run into Hoke’s book is what you need not another failed expieriment.

Stoneman

I hope this helps you find your answer.


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## Stoneman

To everyone who was so kind in assisting me, I want to offer a sincere thanks. Following many of your recommendations, I was able to salvage all the gold from the gold-fill batch that I had made a mistake on. 

Thank you all again for assisting me and I will not make the same mistakes a second time.


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## cly9412

Dr. Poe said:


> One can also precipitate a sol of gold by simply changing the pH to just the other side of 7. From acidic to just alkaline or from alkaline to just acidic. You can expect some base metal hydrated oxides on the alkaline side to co-precip, insol acid salts on the acid side. Mainly I want you guys to see these pics. I know some of you will groan. Hopefully, a lot of you will have catch basins that can be re-worked for gold sols. When I get some pics of the platinum group sol's, I will post them too.
> It's feels good to be appreciated.
> PS: GEO: Never use concentrated ammonium hydroxide or ammonia to a gold solution. There is an extreme danger of explosion. Never let a spent solution sit overnight with any ammonia salt. The Christmas ornament industry has recorded several deaths from this problem as well as formaldehyde and formic acid. They since then have used electrodeposition to glean all spent solutions. Saves lives and brings in a little bit more money.
> I would sure like to discuss with someone the Christmas ornament business. Any of you guys in that business?
> Dr. Poe


Are you saying not to add ammonium hydroxide to wash my gold mud.


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## qst42know

Gold precipitate (mud) is entirely different than gold in solution.


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## Dr. Poe

:shock: Could the mud have any gold oxide or other gold salts mixed with it? Why would anyone take such a chance? If you are trying to recover some silver chloride from the mud, dilute ammonium hydroxide works well enough. Why take a chance with strong ammonia? Even gamblers know that eventually 'snake eyes' will roll. Dr. Poe :|


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## qst42know

Good point I haven't worked with anything stronger than the dilute household ammonia.


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## samuel-a

Dr. Poe said:


> Could the mud have any gold oxide or other gold salts mixed with it?



Do you see any chance of them still being there after several HCl washes/boils?
I have doubts about that.


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## Golddigger1214

Ok so the OP actually asked a question i need the answer to as well, but I need a simple man's explanation. I used HCL/ peroxide 3:1 ratio to remove the gold from pins, fingers, chips. I then filtered the solutionand put all the gold stuff into a hcl/ bleach solution and let it sit for something like 4 hours make a little more the added sodium metabisulfite and let it sit for 10 hours and all I have at the bottom is white stuff. How do I fix this? Its been in there like that for a couple of days now. I just want to know if I can get the gold out and how. Thanks in advance.


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## butcher

White powders will be salts of the acids and metals involved the most common you may be dealing with may include salts of copper I chloride (CuCl), silver chloride (AgCl), lead chloride (PbCl2), sodium chloride (NaCl).

Sodium chloride NaCl (table salts) are fairly water-soluble and will dissolve about the same in hot or cold water. You can use cold water to dissolve NaCl.

Lead chloride PbCl2 is not very soluble in cold water but becomes much more soluble in very hot water.
Use hot water to dissolve (letting this wash water cool and lead chloride to precipitate after decanting the same wash water can be re-heated and reused to remove more of the lead salts saving you on the toxic waste volume to be dealt with later...

Copper I Chloride (CuCl) is not soluble in water but will dissolve in HCl.

Silver chloride (AgCl) is not soluble in water cold or hot, will not dissolve in HCL, when washed of excess acids, and sitting in the sun will darken as its surface reduces to silver.

Because the silver chloride salts do not dissolve to any extent in the acids that will dissolve gold, we can dissolve the gold from the silver salts without putting silver into the solution to any extent with our gold.

We could attempt to dissolve the silver salts with thiosulfates or with ammonia (which can be dangerous of forming explosive salts if not done properly and acidified properly afterward), but there is generally no need to dissolve these salts to recover the gold from them.


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## Golddigger1214

Wow thank you for your detailed information. But I still need to know how I get the gold out of the solution. I'm not seeing any mixed in with the white salts so am I correct in understanding that its in the liquid? Or are you saying its in the salts? If its in the salts then your explanation is basically telling me how to get the salts out of the solution to then reprocess am I correct in that understanding?


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## butcher

Gold will not make white salts under the conditions we are dealing with.

If gold is involved in the white salts it will be visible flakes of gold or it will be in the form of brown precipitated powders which cemented out of solution from the other base metals involved...
Gold is insoluble in water hot or cold, it will not dissolve in HCl (without oxidizers), (review the washes of the white salts described above) gold can be dissolved from any of the remaining silver chloride salts or reduced silver...

If gold is in the solution as gold chlorides you can test for it with a crystal of ferrous sulfate (copperas)which can be made with 10% H2SO4 and iron, testing drops of solution in a spot plate or white plastic spoon looking for a brown ring of precipitated gold...
Or 
You can use the stannous chloride test (tin chloride) (SnCl2) (tin dissolved in HCl) to test a drop of solution (free of oxidizers) using a spot plate or Qtip, paper towel, looking for a violet reaction of colloidal gold called purple of Cassius...


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## Golddigger1214

Ok. Thank you. I'm going to run a test to verify the gold is in the solution and the go from there. The original test showed gold was in the solution, but then the white crystals happened instead of the brown powder so I panicked and hit the forum. Obviously I made an error somewhere ill test and review my steps taken to get here. If the test is positive for gold, should I simply do the sodium metabisulfite again, or is there another route I should be taking?


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## Martijn

The deatailed info butcher gives is intended to make you think about what you are doing in ways you don't understand yet, to spark your interest and do your own research. 
Study Hoke's book and it will make a lot more sense and will help you recover gold in a better way. 

Filter between steps. The reason we treat the gold plated items with acids is to be able to separate the gold from the base metals by selective dissolution, rinsing and filtration. 

You don't want any insoluble metal salts in with dropped gold.
Before you do any dropping with SMB, cool and filter first. 
Cooling with some ice cubes will force more (base-) metal salts out of solution to be captured by a filter. Be careful dropping them in. Let them slide in. 

Save the filters for later recovery of traces of gold.

Martijn.


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## Golddigger1214

Thank you! Wow this site is absolutely amazing. Not at all what I expected. Some other sites should really take notes and follow your lead. I have gotten about a quarter through hokes book. I wanted to do a couple of tests to see if my set up and understanding was correct in a couple of things. I keep all filters they have their own jar. Lol I think when I transferred the gold from the first wash to the second that I should have rinsed a few more times and I don't believe I let it cool first. I was a bit too excited that I did the first step correctly that I rinsed maybe twice then went to the second wash/dissolving solution. And I'm fairly certain that I was a bit over zealous with the SMB. I will hit the books some more and study the info on this site. Theres a lot of idiots out there posting on YouTube and the like that leave a lot of info and parts out of their posts. They should have their videos and posts taken down. People can and I'm sure have gotten hurt trying to follow those. I almost was one of them and then happened upon this site when a question of could I mix together all scrap in one mixture came up. Apparently not. Lol its better to keep stuff separated and as clean as possible. And no one should ever try using lysol toilet bowl cleaner and peroxide to remove gold from anything. Its a huge mess and honestly a total waste of time and scrap. It works but saturates your stuff in suds. Anyways. Thanks again for the help and advice.


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## AJLnz

I have the same problem.
I used hydrochloric acid and sodium hypochlorite acid on a roasted refractory gold ore directly.
The ore was roasted at 650 degrees C for half an hour and cooled before it was submerge with acid mix. Kept it in for 4 hours and adding 15ml sodium hypochlorite every 20 minutes to keep oxidation at 1100mV. No heat added.
Precipitated with metabisulfide mixed in water. 
Solution was a nice yellow and turned dark blood orange and back to yellow.
After an hour it turned milky white and dropped, please see photo.


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