# Thiosulfate (replacment process)



## Anonymous (Jun 7, 2009)

Hello Everyone,

I am new to the forum, as of today, so I apologize if this has been covered before. I looked into partnering with a major source for electronic computer scrap. However, my concern has always been the chemical(s) and processes used in the procedure. This prompted me to do some research, and I found a University, that was experimenting with thiosulfate as a replacement for cyanide.

I do have a pdf file I would be glad to share. I have built a database of information on everything from mining, leaching, etc.

Does anyone know anything about the thiosulfate process. I will dig through my info and try to find the University to check the progress. There is a big movement against some of these more toxic levels and it seemed that this was getting a lot of attention.



Thanks
William


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## goldsilverpro (Jun 7, 2009)

Welcome to our Community, William. I think you'll like it here.

Thanks for the thiosulfate file. It looks good but I haven't had a chance to read it.

Chris


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## Anonymous (Jun 7, 2009)

Thank you,

I like what I see already. I have tons of info and docs I have collected over the past year or so. I am a research junkie. Now that I have found a home with like minded individuals, I will go through what I have and share any pertinent data.

Thanks again for the welcome.

William


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## Anonymous (Jun 7, 2009)

Here is the link where I first heard of the thiosulfact process.

http://www.chem.monash.edu.au/staff/spiccia/gold.html


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## cad (Jun 25, 2009)

Hello all, 
I am also new to this Forum. I have been doing a bit of refining, assay, leaching, smelting, etc. I have started using sodium thiosulfate and ammonium sulfate to do ore leaching with pretty good success (non hazmat). Easy to dispose of when it is spent just bring it to a ph 7 and make sure contaminants are locked up. I have not used it on scrap yet. I have also read that they use injections of tiosufate to help with cyinide and arsnic poisoning ( i dont know all the details)

I need some help with making shot for refining.

Thank you,
Carl


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## Oz (Jun 25, 2009)

Shot, or do you mean cornflakes? The thinner cornflakes aid in acid digestion of the material being refined and shot is typically made of your finished product for sale to the jewelry trade.

edit for spelling


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## Platdigger (Jun 25, 2009)

I am curious about the Thio. Have you found a good cheap source of the chemicals involved?
Thanks, and welcome to the forum.


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## goldsilverpro (Jun 25, 2009)

Tech or Photo grade Na2S2O3.5H2O is fairly cheap. Here's the first one I found - $2/pound in 55 pound lots. Look around and you can probably find it cheaper.
http://www.koidepot.com/KDSD-Sodium-Thiosulfate-KDSD-Pond-Products-sc-608.html:


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## Platdigger (Jun 25, 2009)

Thank You Chris.

Carl, since a 20% solute of ammonium sulfate has a PH of 4.8......do you do you do your leaching on the acidic side?
Randy


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## cad (Jun 26, 2009)

Hello thanks your your replies!

Yes i need to make corn flakes for nitric acid. I need to reduce dore bars for processing.

The thio Leach i use Three parts sodium thiosulfate (one source the chemistry store.com) 67.50 for 50 lbs One part ammonium sulfate granular (fertilizer) a buffer i am working on a good source. Use adjust ph to 9.2-10 with household amonia. and leach with air, ozone, mix, some heat 120. i have had good results on ores. All non haz mat! 

I am fairly new at this and am discovering so many things on a daily basis. This forum im hoping will help share great ideas and new twists on the subject! :lol:

Thanks,
Carl


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## Platdigger (Jun 26, 2009)

Thanks for the Thio info..... :lol: 

As for "cornflakes" it is just a mater of pouring molten gold from a melting dish into cold water.

What is the percentage of gold in your dore?

If it is too high, you will need to "inquart" before treatment with nitric.
Randy


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## cad (Jun 26, 2009)

Hello Randy, 
i have more of a mix of platinum group with some gold present. when i smelt ore cons i use a lead based flux(at this time) into a dore hershey kiss type. I also fuse my filters by smelting with a lead based flux and pour it on an alluminum plate pouring the slag to the side cools very rapidly. using big fans and working outside. but now comes the next stage preparing to separate and persipitate!! Do you personally use nitric acid substitute (sodium nitrate and sulfuric) or the real thing!!

Thanks,
Carl


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## Harold_V (Jun 27, 2009)

Carl,

Do I understand you correctly, that the material you reference as doré contains lead?

If that be the case, you do NOT want to start processing with nitric. It is important that you eliminate the lead first. Cupellation is generally the process involved. 

If you have silver mixed with platinum, you're going to experience something you may not have expected. Platinum will follow your silver, for it will dissolve in nitric acid alone when in the presence of silver. It can be recovered with copper, along with the silver, or you can precipitate the silver as chloride, then wash the still dissolved platinum from the silver chloride. In any case, unless you have a substantial amount of platinum in solution, you won't be able to precipitate it directly, so allowing it to follow your silver is a good way to make a recovery. By parting the silver in a cell, it will get concentrated to the point where you can effect a recovery. 

I strongly recommend you read Hoke's book if you have not thus far. 

Harold


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## cad (Jun 27, 2009)

Hello Harold, 

I have not read this book what is the title so i can look it up.

I thought only Palladium disolved in the nitric acid along with silver, and the lead, and could be percipitaited with dmg after you remove silver chrolide with salt. 

In cupeling it seems often that the platinum goes into the cupel and is hard to get out with out inquarting.

It seems that if you put the lead/noble alloy in nitric that the solution becomes saturated maybe this is just a matter of how much solution that you use. I am open to any ideas that have worked better!! as i said i am new to this.

thanks,
Carl


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## goldsilverpro (Jun 27, 2009)

An old assay method of separating Au and Pt is to dissolve most all of the Pt away from the gold by adding silver, cupelling, and parting in nitric. This has to be repeated at least 3 times and you still won't remove 100% of the Pt - close, but not quite. The ratio of silver to Pt should be from 12-15/1, in order to dissolve the most Pt at each parting. With a large amount of Pt, the nitric solution will turn black from colloidal Pt. 

When platinum is alloyed with other metals, such as Cu, Pb, or Zn, some of the Pt will also dissolve in nitric. 

If hot, nearly concentrated, sulfuric parting is used, the Pt won't dissolve in the presence of silver. This is the method I preferred.


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## Harold_V (Jun 27, 2009)

cad said:


> Hello Harold,
> 
> I have not read this book what is the title so i can look it up.


The book title is Refining Precious Metal Wastes. One of the readers will step forward and provide a link for a download, or you can purchase a hard copy by following this link:

http://www.gesswein.com/catalog/catalog.cfm?cat=12&sub=3&subsub=59&catalog=1&CFID=1471004&CFTOKEN=30985426 

I highly recommend you purchase a copy. The book launched my refining career. I had absolutely NO knowledge of chemistry, yet went on to operate a commercial refining business that was my sole source of income for more than ten years. How does one place a value on a book when such a small investment has the potential to elevate one to such a level?



> I thought only Palladium dissolved in the nitric acid along with silver, and the lead, and could be percipitaited with dmg after you remove silver chrolide with salt.


What you _don't _ want to do is recover palladium with dmg. Slight traces of palladium will create huge volumes of bright canary yellow precipitate which is sticky and very difficult to handle. DMG is an excellent testing reagent, but not so good for recovery. It works, but the problems I outlined are troublesome. It's also quite expensive. 

Lead dissolved in nitric will precipitate from solution of its own accord (as lead nitrate) as the solution cools. Therefore, if you are dealing with silver, the lead has the potential to follow the silver, or other elements that you recover. It should be eliminated before dissolving values. It is soluble, at least to some degree, in hot water, so it can be removed with careful washing. 

If cupellation is not an option, you may experience successful results by the addition of sulfuric, which will precipitate the lead as a sulfate. It can then be filtered from the solution. Due to lead's potential to contaminate and destroy the properties of precious metals, I would recommend you eliminate it as early in the process as is possible. 



> In cupeling it seems often that the platinum goes into the cupel and is hard to get out with out inquarting.


I won't be any help here. I have extensive experience in refining metals, but have no experience in assaying. I paid for what little I needed, not having the required equipment to perform my own. Sorry. 



> It seems that if you put the lead/noble alloy in nitric that the solution becomes saturated maybe this is just a matter of how much solution that you use. I am open to any ideas that have worked better!! as i said i am new to this.


Not quite sure what you mean, here. My experience dictates that the saturation point of most of these solutions is far greater than you might imagine. I worked with hot solutions, _always_, so I experienced crystal growth as solutions cooled on occasion, but found that the amount of nitric used was the major factor. If you are dissolving alloys that contain many elements, you are likely exhausting the nitric, not saturating solutions. Could be wrong----but it's worth exploring. 

Sorry I'm not more help. I worked, primarily, with scrap metals, only rarely with values recovered from ores. None of my experiences yielded problems similar to yours. 

Harold


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## cad (Jun 28, 2009)

Wow great info :lol:

I will get this book.

For now i need to use lead for most of my assay work and smelting as it involves lead. If i make as many exposed surfaces as possible (corn flakes) and disolve in an acid. Now the acid part. Do you know if using nitrc sub. (sulfuric/sodium nitrate) will help in my first parting rather than straight nitric since it contains sulfuric or perhaps i does not work that way. 

After that using AR cold then hot etc to part gold, pt, rhodium etc. :?: 

As i learn and develope this process i will continue to leach, filter, electrowinn, and percipitate my nobles and smelt into dore pieces. Do you have any coments or suggestion on these types of steps.

I also would like to find a good refiner to get some of my assets turned into funds. I need some crushers and fine grinders to do a larger amount of materials. Any suggestions or sources.

thanks,
Carl


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## Anonymous (Jun 28, 2009)

I think the sulfuric/sulfate causes problems with lead as it forms lead sulfate, insoluble and a pain to seperate. 

Jim


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## Harold_V (Jun 29, 2009)

cad said:


> Do you know if using nitrc sub. (sulfuric/sodium nitrate) will help in my first parting rather than straight nitric since it contains sulfuric or perhaps i does not work that way.


I am of the opinion that the resulting solution no longer should be considered sulfuric, but I am not a chemist and may be wrong. I also have no experience with the material. My entire refining career revolved around processing with commercially prepared acids, so I am not the least bit familiar with the home made varieties. 



> After that using AR cold then hot etc to part gold, pt, rhodium etc. :?:


That's correct. The idea is to eliminate as much of the base metal as you can before dissolving the values. The volumes of solutions you would deal with would be much smaller, and the quality of the recovered values will be far greater. Remember, when you're refining, the ultimate goal is to achieve a high level of purity of the recovered metals. Eliminating anything of little or no value early in the process makes your chore easier. 



> As i learn and develope this process i will continue to leach, filter, electrowinn, and percipitate my nobles and smelt into dore pieces. Do you have any coments or suggestion on these types of steps.


Because I rarely worked with ores, I have little to offer. My limited experience was with an ore that most only dream of---assaying at over 300 troy oz/ton gold plus more than that in silver. Only a small lot, (four 5 gallon buckets worth), but a tremendous learning experience. 



> I also would like to find a good refiner to get some of my assets turned into funds. I need some crushers and fine grinders to do a larger amount of materials. Any suggestions or sources.


I think you are better served to rely on information from others that are currently involved in selling their values. I have been away from refining too long to have any sources I'd recommend. 

One thing I would offer you, and it won't go down well. I'm sure. The idea of producing much of the platinum group metals isn't likely. They are generally not found in great quantity in the US. I recommend you think carefully when anyone suggests to you that you are making a recovery of any of them in anything more than trace amounts. If you are, you are the rare exception. 

Luck!

Harold


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## Platdigger (Jul 11, 2009)

Chris, you said: 
"If hot, nearly concentrated, sulfuric parting is used, the Pt won't dissolve in the presence of silver. This is the method I preferred."

Question, what concentration of sulfuric?

As concentrated boiling sulfuric will disolve nearly every metal but gold.
Randy


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## goldsilverpro (Jul 13, 2009)

Platdigger,

The standard sulfuric parting starts with a solution of 100ml concentrated H2SO4 + 22 ml distilled water (90%, by weight, boiling point = 504 F). A second parting uses a solution of 100ml H2SO4 + 10ml distilled water (95% by weight, boiling point = 563 F). Both are used very hot - near boiling, but not quite. The first parting is very slow and is used to prevent the Pt and Au from breaking up. The second is much faster. Some people use only the 95%. These solutions will dissolve Ag and Pd but not Au or Pt.

Two containers of pure tin and pure bismuth are placed on the hot plate to control the temperature. Tin melts at 450F and bismuth at 520F. The 90% is heated until the tin melts but the bismuth doesn't. The 95% until the bismuth barely melts. I think we used to put these metals in Coors porcelain crucibles. It's been a long time since I've done this.

These figures came from "A Textbook of Fire Assaying" by Bugbee. They are based on using reagent grade sulfuric. Technical grade is usually a percent or two weaker to start with. I used only the 95% sulfuric.

These are only the basics. There are detailed ways to rinse out the silver sulfate and to remove traces of lead retained in the assay beads. Etc.


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