Shunter421
Member
thank you for your response yes i understand that there will be more gold inside the chips and ram i have a jaw crusher which im going to crush to the internal gold
thank you
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" Help ! Have a deplating set up but cant get good yeild"
- Thread starter Shunter421
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thank you
Aqua Regia is not suited to strip plating.
So you say that you are supposed to use Zinc and Ascorbic Acid?
Strange.
There are many processes that dissolves the Gold.
As long as it is acidic you have many ways to get rhe Gold out.
There is a thread from Deano discussing several among them "Neutral Saline Hypochlorite".
Cheap but I'm not sure of the speed.
haveagojoe
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Personally I would not attempt to use a different method in a machine which it's not designed for, especially such an expensive one. I'd want to figure out the intended method. I would not worry about yields until the exact process can be established.
After reading more I am inclined to think (guess) that it is a form of Sodium Thiosulfate leach. There are some advantages to this process, as in itself Sodium Thiosulfate is non-toxic. The chemicals required are likely much cheaper than conventional acid-based processes. It also strips gold very quickly, faster than cyanide.
Again, the best course of action would be to obtain the information about the chemicals from the supplier, and if that is not possible then to do more thorough tests to find out what they are. At the very least, do litmus tests to determine whether your solution is acid or akaline. If possible take them to an analyst.
In the meantime I would be reading up about the various sulfur-based approaches. In my unprofessional (total amateur) opinion the process synthesises Sodium Thiosulfate from Sodium Bisulfate, Sodium Hydroxide and Sulfur in the mixing tank. However this is quite far out of my wheelhouse as I have no experience with Sulfur-based approaches.
After reading more I am inclined to think (guess) that it is a form of Sodium Thiosulfate leach. There are some advantages to this process, as in itself Sodium Thiosulfate is non-toxic. The chemicals required are likely much cheaper than conventional acid-based processes. It also strips gold very quickly, faster than cyanide.
Again, the best course of action would be to obtain the information about the chemicals from the supplier, and if that is not possible then to do more thorough tests to find out what they are. At the very least, do litmus tests to determine whether your solution is acid or akaline. If possible take them to an analyst.
In the meantime I would be reading up about the various sulfur-based approaches. In my unprofessional (total amateur) opinion the process synthesises Sodium Thiosulfate from Sodium Bisulfate, Sodium Hydroxide and Sulfur in the mixing tank. However this is quite far out of my wheelhouse as I have no experience with Sulfur-based approaches.
Shunter421
Member
Thank you for your help much appreciated
Only this thread in my email today , so getting a late start .
Did not fully read all replies - I did do a quick scan of all .
So not sure of repeats , or if you took in what I thought of .
Like at least on reply mentioned the vast majority of recoverable gold is inside the chips ,
Like any process finding what the least cost to you because of cost or available supplies & equipment .
I would suggest starting with classifying the different sources , gold plated items , chips - removed from boards etc.
Pyrolysing - heating / burning to at least gray if not white in color .
Or wet-ashing process - chemicals that you can access ---- which ever is cheaper for you & where you are .
My understanding is the bond wires in chips will run about 22 carat --- so doing separately , from other products that depending on process my be alloyed with other metals .
After heating , burning or wet-ashing , then its a simple gravity seperation , much like a sluice box , like in placer mining .
Did not fully read all replies - I did do a quick scan of all .
So not sure of repeats , or if you took in what I thought of .
Like at least on reply mentioned the vast majority of recoverable gold is inside the chips ,
Like any process finding what the least cost to you because of cost or available supplies & equipment .
I would suggest starting with classifying the different sources , gold plated items , chips - removed from boards etc.
Pyrolysing - heating / burning to at least gray if not white in color .
Or wet-ashing process - chemicals that you can access ---- which ever is cheaper for you & where you are .
My understanding is the bond wires in chips will run about 22 carat --- so doing separately , from other products that depending on process my be alloyed with other metals .
After heating , burning or wet-ashing , then its a simple gravity seperation , much like a sluice box , like in placer mining .
haveagojoe
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ChatGPT seemed to think my sodium thiosulfate theory is plausible, below is a summary of conclusions from the discussion. (Disclaimer: ChatGPT is far from infallible, this is just intended as a conversation starter when OP engages with a professional advisory chemist.)
Chemical A is most likely sodium hydroxide (NaOH).
Chemical B is likely sodium sulfide (Na2S) or sodium polysulfide (Na2Sx), with lead either as a contaminant or part of a stabilizer.
Chemical C could be sodium hydrosulfide (NaHS) or elemental sulfur (S8).
The trace elements observed in the XRF readings may be explained if they were sourced from naturally occurring mineral deposits, geothermal brines, or evaporites. For example, lead, copper, and iron in Chemical B suggest it may come from sulfide ores or industrial byproducts rather than being a highly purified reagent. Sodium, chlorine, and sulfur in Chemical C suggest it could be derived from natural sulfur deposits or geothermal brines. Trace elements like magnesium, aluminum, silicon, calcium, zirconium, and molybdenum are commonly found in natural mineral formations and brine deposits. However, if the chemicals were synthetically manufactured, the impurities could come from raw materials, industrial processing methods, or contamination during storage and handling.
If chemical B is sodium sulfide (Na2S), it reacts with sodium hydroxide to form sodium thiosulfate in the following reaction:
2NaOH + Na2S + S → Na2S2O3 + H2O
If chemical B is sodium polysulfide (Na2Sx), the reaction can be written as:
NaOH + Na2Sx + (x−2)S → Na2S2O3 + Na2Sx−2
Gold is then dissolved into solution through complexation with thiosulfate, forming a stable gold-thiosulfate complex according to the equation:
4Au + 8Na2S2O3 + O2 + 2H2O → 4Na3[Au(S2O3)2] + 4NaOH
Gold is precipitated from the thiosulfate solution by reducing Au3+ to metallic gold in fine black particles. During this process, thiosulfate (S2O32-) converts to sulfite (SO32-) as a byproduct, and the reaction proceeds as follows:
2[Au(S2O3)2]3− + 6NaOH + 3Na2S → 2Au0 + 3Na2S2O3 + 3Na2SO3 + 3H2O
If excess sulfide is present, gold can precipitate as gold sulfide (Au2S3), which is also black. In this case, the reaction follows:
2[Au(S2O3)2]3− + 3Na2S + 6NaOH → Au2S3↓ + 6Na2S2O3 + 3H2O
Sodium sulfide (Na2S) is the preferred precipitant for metallic gold (Au0) recovery, while sodium hydrosulfide (NaHS) may favor gold sulfide (Au2S3) formation.
Maintaining the proper pH is crucial to the process. A pH range of 9 to 10 is optimal for the stability of gold-thiosulfate complexes. If the pH drops below 8.5, thiosulfate becomes unstable and begins to decompose, primarily forming elemental sulfur (S) and sulfur dioxide (SO2). In the presence of excess sulfide (S2−) or under certain conditions, toxic hydrogen sulfide (H2S) gas may also be released. If the pH rises above 10.5, gold remains in solution, reducing precipitation efficiency. To avoid these issues, sodium hydroxide should be added gradually while monitoring pH with a meter rather than relying on pH strips.
To recover any remaining gold in solution, zinc dust is added to reduce the gold-thiosulfate complex back to metallic gold. The reaction follows:
2[Au(S2O3)2]3− + 3Zn → 2Au + 3ZnS2O3
This reaction takes five to six hours, after which the solution is allowed to settle for one to two hours before filtering. The pH should be maintained between 8 and 9 for efficient gold reduction.
One of the main hazards in this process is the potential release of hydrogen sulfide gas (H2S), which is highly toxic and fatal at concentrations of 1000 ppm. Even at low concentrations (as low as 10-20 ppm), it can cause irritation, and at 100-200 ppm, it can lead to serious health effects. To mitigate this danger, the chemicals should be kept away from acids and moisture, and hydrogen sulfide detectors and proper ventilation should be in place.
Impurities such as lead, copper, and iron sulfides may co-precipitate with gold, reducing its purity. This can be addressed by pretreating the solution with EDTA, a chelating agent, to remove base metals before gold precipitation. Controlled aeration can help oxidize unwanted sulfide impurities before gold is precipitated. After precipitation, the black gold powder should be thoroughly washed with hot dilute ammonium thiosulfate to remove excess sulfides and improve purity.
This process requires careful pH control, proper handling of sulfide chemicals, and strict safety precautions to minimize the risks associated with hydrogen sulfide gas.
The disposal of thiosulfate-containing solutions should be done carefully. Thiosulfate can degrade into sulfate and sulfite, which are less hazardous, but the presence of residual sulfide and heavy metals may require neutralization or filtration before disposal.
While zinc is a common choice for gold recovery, other reducing agents such as iron (Fe) or sodium borohydride (NaBH4) could also be explored depending on cost, availability, and process efficiency. Iron could be used in the form of steel wool, in a process which involves both chemical reduction and adsorption, where the gold particles adhere to the steel surface. In this case, the formula for reduction follows:
2[Au(S2O3)2]3− + 3Fe → 2Au + 3Fe(S2O3)2
The adsorption effect can enhance recovery efficiency by capturing fine gold particles that might otherwise remain in solution. Once gold is deposited onto the steel wool, it needs to be separated, typically by burning the steel wool in a controlled environment, leaving behind a gold-rich residue that can be further refined by smelting or acid digestion.
Steel wool was favored for cementation of gold from thiosulfate solutions by the infamous Dr Poe, as discussed on page 3 of this fascinating thread: https://goldrefiningforum.com/threads/thiosulphate-dropped-testing-for-pm.12284/
I asked ChatGPT to produce instructions for performing the process; the response was as follows:
Chemical A is most likely sodium hydroxide (NaOH).
Chemical B is likely sodium sulfide (Na2S) or sodium polysulfide (Na2Sx), with lead either as a contaminant or part of a stabilizer.
Chemical C could be sodium hydrosulfide (NaHS) or elemental sulfur (S8).
The trace elements observed in the XRF readings may be explained if they were sourced from naturally occurring mineral deposits, geothermal brines, or evaporites. For example, lead, copper, and iron in Chemical B suggest it may come from sulfide ores or industrial byproducts rather than being a highly purified reagent. Sodium, chlorine, and sulfur in Chemical C suggest it could be derived from natural sulfur deposits or geothermal brines. Trace elements like magnesium, aluminum, silicon, calcium, zirconium, and molybdenum are commonly found in natural mineral formations and brine deposits. However, if the chemicals were synthetically manufactured, the impurities could come from raw materials, industrial processing methods, or contamination during storage and handling.
If chemical B is sodium sulfide (Na2S), it reacts with sodium hydroxide to form sodium thiosulfate in the following reaction:
2NaOH + Na2S + S → Na2S2O3 + H2O
If chemical B is sodium polysulfide (Na2Sx), the reaction can be written as:
NaOH + Na2Sx + (x−2)S → Na2S2O3 + Na2Sx−2
Gold is then dissolved into solution through complexation with thiosulfate, forming a stable gold-thiosulfate complex according to the equation:
4Au + 8Na2S2O3 + O2 + 2H2O → 4Na3[Au(S2O3)2] + 4NaOH
Gold is precipitated from the thiosulfate solution by reducing Au3+ to metallic gold in fine black particles. During this process, thiosulfate (S2O32-) converts to sulfite (SO32-) as a byproduct, and the reaction proceeds as follows:
2[Au(S2O3)2]3− + 6NaOH + 3Na2S → 2Au0 + 3Na2S2O3 + 3Na2SO3 + 3H2O
If excess sulfide is present, gold can precipitate as gold sulfide (Au2S3), which is also black. In this case, the reaction follows:
2[Au(S2O3)2]3− + 3Na2S + 6NaOH → Au2S3↓ + 6Na2S2O3 + 3H2O
Sodium sulfide (Na2S) is the preferred precipitant for metallic gold (Au0) recovery, while sodium hydrosulfide (NaHS) may favor gold sulfide (Au2S3) formation.
Maintaining the proper pH is crucial to the process. A pH range of 9 to 10 is optimal for the stability of gold-thiosulfate complexes. If the pH drops below 8.5, thiosulfate becomes unstable and begins to decompose, primarily forming elemental sulfur (S) and sulfur dioxide (SO2). In the presence of excess sulfide (S2−) or under certain conditions, toxic hydrogen sulfide (H2S) gas may also be released. If the pH rises above 10.5, gold remains in solution, reducing precipitation efficiency. To avoid these issues, sodium hydroxide should be added gradually while monitoring pH with a meter rather than relying on pH strips.
To recover any remaining gold in solution, zinc dust is added to reduce the gold-thiosulfate complex back to metallic gold. The reaction follows:
2[Au(S2O3)2]3− + 3Zn → 2Au + 3ZnS2O3
This reaction takes five to six hours, after which the solution is allowed to settle for one to two hours before filtering. The pH should be maintained between 8 and 9 for efficient gold reduction.
One of the main hazards in this process is the potential release of hydrogen sulfide gas (H2S), which is highly toxic and fatal at concentrations of 1000 ppm. Even at low concentrations (as low as 10-20 ppm), it can cause irritation, and at 100-200 ppm, it can lead to serious health effects. To mitigate this danger, the chemicals should be kept away from acids and moisture, and hydrogen sulfide detectors and proper ventilation should be in place.
Impurities such as lead, copper, and iron sulfides may co-precipitate with gold, reducing its purity. This can be addressed by pretreating the solution with EDTA, a chelating agent, to remove base metals before gold precipitation. Controlled aeration can help oxidize unwanted sulfide impurities before gold is precipitated. After precipitation, the black gold powder should be thoroughly washed with hot dilute ammonium thiosulfate to remove excess sulfides and improve purity.
This process requires careful pH control, proper handling of sulfide chemicals, and strict safety precautions to minimize the risks associated with hydrogen sulfide gas.
The disposal of thiosulfate-containing solutions should be done carefully. Thiosulfate can degrade into sulfate and sulfite, which are less hazardous, but the presence of residual sulfide and heavy metals may require neutralization or filtration before disposal.
While zinc is a common choice for gold recovery, other reducing agents such as iron (Fe) or sodium borohydride (NaBH4) could also be explored depending on cost, availability, and process efficiency. Iron could be used in the form of steel wool, in a process which involves both chemical reduction and adsorption, where the gold particles adhere to the steel surface. In this case, the formula for reduction follows:
2[Au(S2O3)2]3− + 3Fe → 2Au + 3Fe(S2O3)2
The adsorption effect can enhance recovery efficiency by capturing fine gold particles that might otherwise remain in solution. Once gold is deposited onto the steel wool, it needs to be separated, typically by burning the steel wool in a controlled environment, leaving behind a gold-rich residue that can be further refined by smelting or acid digestion.
Steel wool was favored for cementation of gold from thiosulfate solutions by the infamous Dr Poe, as discussed on page 3 of this fascinating thread: https://goldrefiningforum.com/threads/thiosulphate-dropped-testing-for-pm.12284/
I asked ChatGPT to produce instructions for performing the process; the response was as follows:
Gold Recovery Using the Thiosulfate Process: Step-by-Step Instructions
Safety Precautions
- Work in a well-ventilated area or a fume hood.
- Wear personal protective equipment (PPE), including gloves, safety goggles, and a respirator rated for hydrogen sulfide (H₂S) gas.
- Keep acids away from sulfide-containing solutions to prevent toxic H₂S gas release.
- Monitor pH levels carefully to avoid decomposition of thiosulfate and unwanted side reactions.
- Have emergency equipment (neutralizing agents, spill kits, and an H₂S detector) readily available.
Materials and Equipment
Chemicals Required
- Sodium hydroxide (NaOH)
- Sodium sulfide (Na₂S) or sodium polysulfide (Na₂Sₓ)
- Sulfur (S₈) (if using sodium polysulfide)
- Thiosulfate source (Na₂S₂O₃) (may form in situ)
- Zinc dust (Zn) or steel wool (Fe) for gold precipitation
- EDTA (optional, for removing base metals)
- Distilled water
Equipment Needed
- Glass or plastic reaction vessel (no metal containers)
- pH meter (preferred) or high-precision pH strips
- Magnetic stirrer or mechanical stirrer
- Filtration system (Büchner funnel with vacuum, or fine mesh filter paper)
- Drying oven or heat lamp (optional, for drying gold powder)
Procedure
1. Preparation of the Leaching Solution
- Dissolve sodium hydroxide (NaOH) in distilled water to create a 10% NaOH solution. Stir until fully dissolved.
- If using sodium sulfide (Na₂S):
- Slowly add Na₂S to the NaOH solution while stirring.
- If necessary, adjust pH to 9–10 using additional NaOH.
- If using sodium polysulfide (Na₂Sₓ):
- Add elemental sulfur (S₈) to Na₂S in NaOH solution. Stir continuously until sulfur dissolves.
- Maintain a temperature of 40–50°C to speed up dissolution.
- Adjust pH to 9–10.
2. Leaching Gold into Solution
- Add gold-bearing material to the solution.
- Stir continuously while maintaining a pH of 9–10. Monitor and adjust with NaOH as needed.
- Allow the reaction to proceed for 12–24 hours, ensuring oxygen is present to facilitate gold dissolution:4Au+8Na2S2O3+O2+2H2O→4Na3[Au(S2O3)2]+4NaOH4Au + 8Na₂S₂O₃ + O₂ + 2H₂O → 4Na₃[Au(S₂O₃)₂] + 4NaOH4Au+8Na2S2O3+O2+2H2O→4Na3[Au(S2O3)2]+4NaOH
- Periodically check for the presence of gold in solution using a test reagent (e.g., stannous chloride).
3. Precipitation of Gold
- Filter out any remaining solids to obtain a clear gold-thiosulfate solution.
- If necessary, pretreat with EDTA to chelate base metals.
- Precipitate gold using either:
a) Zinc Dust Method- Add zinc dust while stirring.
- Allow the reaction to proceed for 5–6 hours:2[Au(S2O3)2]3−+3Zn→2Au+3ZnS2O32[Au(S₂O₃)₂]³⁻ + 3Zn → 2Au + 3ZnS₂O₃2[Au(S2O3)2]3−+3Zn→2Au+3ZnS2O3
- Let the precipitated gold settle for 1–2 hours.
b) Steel Wool (Iron) Method
- Add steel wool directly into the solution.
- Stir gently for even exposure.
- Gold will adsorb onto the steel surface while iron dissolves:2[Au(S2O3)2]3−+3Fe→2Au+3Fe(S2O3)22[Au(S₂O₃)₂]³⁻ + 3Fe → 2Au + 3Fe(S₂O₃)₂2[Au(S2O3)2]3−+3Fe→2Au+3Fe(S2O3)2
- Once deposition is complete, remove the steel wool and burn it in a controlled environment to recover gold residue.
4. Filtration and Washing
- Filter the gold precipitate using fine mesh filter paper or a vacuum filtration system.
- Wash the precipitate thoroughly with hot distilled water to remove residual thiosulfate.
- Optionally, rinse with a hot, dilute ammonium thiosulfate solution to improve purity.
5. Drying and Refining
- Dry the precipitate under mild heat using an oven (50–70°C) or a heat lamp.
- The dried gold can be smelted or refined using aqua regia for higher purity.
Disposal Considerations
- Neutralization of Waste Solution
- Gradually add hydrogen peroxide (H₂O₂) to oxidize sulfides and reduce toxicity.
- Adjust pH to 7–8 using NaOH or sulfuric acid as needed.
- Filtration of Heavy Metals
- Precipitate heavy metals by adding calcium hydroxide (Ca(OH)₂) or ferric sulfate (Fe₂(SO₄)₃).
- Filter the solids and dispose of according to local environmental regulations.
- Final Disposal
- Ensure that no toxic sulfide compounds remain before discarding.
Conclusion
This method allows for the extraction and recovery of gold with high efficiency while minimizing environmental impact. Proper pH control and safety measures are critical to preventing unwanted side reactions and ensuring worker safety.
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Shunter421
Member
Thank you yes that is the process but it didn’t really seem to get much black dust unfortunately. I have brought some electrowinning machines to run the solution that I have for that I believe has gold in it.
Attached is a pics of my winning machine
Thanks for your reply really appreciate your help
haveagojoe
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You're welcome 
It's possible that some gold remained in solution if the pH was too high. I would recommend testing carefully with a pH meter before and during precipitation. However it's also possible that your estimated yield was a little optimistic. Escrap yields are notoriously difficult to predict and available data is not always reliable. It's best to produce your own yield estimates from your own recovery and base your aquisititon of source material on those.
I also recommend reading the thread I linked although it is very long; much to the ire of other users, Dr Poe caused some controversy by stating that from a thiosulfate solution, gold may be deposited at the anode of an electrowinning cell as well as at the cathode. Perhaps you will be able to determine if he was correct!
I hope you will share your findings with the forum as this process is underdocumented here and shows promise for a more environmentally friendly approach to our classic acid-based chemistries.
It's possible that some gold remained in solution if the pH was too high. I would recommend testing carefully with a pH meter before and during precipitation. However it's also possible that your estimated yield was a little optimistic. Escrap yields are notoriously difficult to predict and available data is not always reliable. It's best to produce your own yield estimates from your own recovery and base your aquisititon of source material on those.
I also recommend reading the thread I linked although it is very long; much to the ire of other users, Dr Poe caused some controversy by stating that from a thiosulfate solution, gold may be deposited at the anode of an electrowinning cell as well as at the cathode. Perhaps you will be able to determine if he was correct!
I hope you will share your findings with the forum as this process is underdocumented here and shows promise for a more environmentally friendly approach to our classic acid-based chemistries.
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haveagojoe
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Chemical A could also be sodium carbonate, in which case the formula would be
Na2CO3+Na2S+S→Na2S2O3+CO2
The traces of calcium and aluminum in the XRF of chemical A may suggest it is Na₂CO₃ sourced from natural soda ash deposits rather than pure NaOH.
However sodium carbonate is a weaker alkali than sodium hydroxide, so it might not be able to maintain a high enough pH at the leaching stage.
You could do a small test by adding a few drops of hydrochloric acid to a sample of chemical A. If it bubbles, that's carbon dioxide being released, in which case it contains sodium carbonate. If it's pure sodium hydroxide, it will simply neutralize the HCl with no gas production.
It's possible that sodium carbonate was chosen because it is a stable powder, while sodium hydroxide absorbs moisture from the air.
It could also be a mixture of both sodium carbonate from natural sources and industrially refined sodium hydroxide.
Na2CO3+Na2S+S→Na2S2O3+CO2
The traces of calcium and aluminum in the XRF of chemical A may suggest it is Na₂CO₃ sourced from natural soda ash deposits rather than pure NaOH.
However sodium carbonate is a weaker alkali than sodium hydroxide, so it might not be able to maintain a high enough pH at the leaching stage.
You could do a small test by adding a few drops of hydrochloric acid to a sample of chemical A. If it bubbles, that's carbon dioxide being released, in which case it contains sodium carbonate. If it's pure sodium hydroxide, it will simply neutralize the HCl with no gas production.
It's possible that sodium carbonate was chosen because it is a stable powder, while sodium hydroxide absorbs moisture from the air.
It could also be a mixture of both sodium carbonate from natural sources and industrially refined sodium hydroxide.
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Shunter421
Member
It seemed to leach the gold
Off fine from
The material
And In like 5 mins it was very fast with no heat but it’s the precipitation was the issue and I don’t feel
That part of the process happened very well
haveagojoe
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My understanding is that it's a two-stage preciptiation, is this correct? Firstly with chemical C (probably sulfur) and secondly with zinc?
Perhaps you could attempt the steel wool method with a small sample of your remaining post-process solution? If there is gold still in it, it may cement onto the steel wool in small but visible clumps.
haveagojoe
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Bear in mind that while escrap may appear to show a lot of visible gold, the plating is incredibly thin, and the gold used in plating is not pure, it's usually only around 14k.
I also find it difficult not to be disheartened when a beaker containing a thick and apparently bountiful layer of foils gives me back only a couple of grams of pure gold for all my work!
Also, as others have mentioned, a large proportion of the gold in RAM is inside the black chips, which need to be pyrolized, then incinerated, and then crushed before it can be recovered. If this was not taken into account when estimating your yield, I'd be quite confident that your missing gold is still in your source material.
And as for CPUs... their content can range from "rather a lot" to "almost none at all" depending on the type and year of manufacture. Again, most of the gold is inside the chip itself.
I also find it difficult not to be disheartened when a beaker containing a thick and apparently bountiful layer of foils gives me back only a couple of grams of pure gold for all my work!
Also, as others have mentioned, a large proportion of the gold in RAM is inside the black chips, which need to be pyrolized, then incinerated, and then crushed before it can be recovered. If this was not taken into account when estimating your yield, I'd be quite confident that your missing gold is still in your source material.
And as for CPUs... their content can range from "rather a lot" to "almost none at all" depending on the type and year of manufacture. Again, most of the gold is inside the chip itself.
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haveagojoe
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At the end of the thread I linked a paper was posted (page 10), but the link no longer works; fortunately the archived contents are still available courtesy of the almighty Wayback Machine:
https://web.archive.org/web/20140714122728/http://www.ejmpep.com/rath_et.al.pdf
The paper discusses the effects and advantages of adding ammonia and copper in thiosulfate processes, which may be significant when attempting to dissolve solid gold such as the bonding wires in IC chips and processors, as opposed to stripping of gold plating.
https://web.archive.org/web/20140714122728/http://www.ejmpep.com/rath_et.al.pdf
The paper discusses the effects and advantages of adding ammonia and copper in thiosulfate processes, which may be significant when attempting to dissolve solid gold such as the bonding wires in IC chips and processors, as opposed to stripping of gold plating.
haveagojoe
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Although I think your missing gold is still in your source material, another possibility could be that colloidal gold was formed during precipitation, which is gold in the form of incredibly fine particles which are small enough to pass through a filter. There are various factors which could cause this, one being that the precipitant was added too quickly; another being contamination, such as with oils from the source material.
A stannous chloride test will only work to detect gold in its ionic form, not in the gold-thiosulfide complex. You can add some HCl to the test sample to break down the complex before performing the stannous chloride test, or alternatively you could test with Dimethylglyoxime, looking for a red or pink color to confirm gold in solution.
If there is colloidal gold, your electrowinning cell should recover it.
A stannous chloride test will only work to detect gold in its ionic form, not in the gold-thiosulfide complex. You can add some HCl to the test sample to break down the complex before performing the stannous chloride test, or alternatively you could test with Dimethylglyoxime, looking for a red or pink color to confirm gold in solution.
If there is colloidal gold, your electrowinning cell should recover it.
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Do really metallic particles with no charge attract to the electrodes in a cell?
haveagojoe
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You're right, I didn't think about that
