# Bombing cyanide solution



## goldnugget77 (Aug 1, 2009)

Hi 

Bombing cynadie solution 
I remember working in a jewelery factory
They did this for every jewelery before polishing

In my opinion most of the times it was not necessary.
A magnetic tumbler usually does the same work.

They saved this cyanide solution in a very large tank.
About 6 feet high 
They electrically extracted the gold from the solution
I didn't know about these kinds of things back then so I am not sure

My question is this
If I have such a cyanide solution 
How would I extract the gold
I looked in the Hoke book and I could not see any info on this

I am guessing that
1) I would be able to do this with an anode and cathode method
2) In the Hoke book she writes about adding something to the cyanide solution to make it acidy 
Something like that.I could use this option to recover the gold


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## jimdoc (Aug 1, 2009)

Did you check C.W. Ammens book? I think it is still available to download on the forum somewhere. I think he goes into more processes and equipment than Hoke.
Jim


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## greentea (Aug 1, 2009)

I asked about this some time ago and was directed to the Hoke book and given some tips by the pro's on this board. I use powdered zinc to drop the gold.


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## goldnugget77 (Aug 1, 2009)

Hi guys
Thanks for your help
Hi greentea
I found that tread it was very helpful


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## goldnugget77 (Aug 1, 2009)

Now that we have started this topic
I worked at another place for a while and they were putting their cyanide solution in the sink
This was about 30 years ago


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## greentea (Aug 1, 2009)

goldnugget77 said:


> Now that we have started this topic
> I worked at another place for a while and they were putting their cyanide solution in the sink
> This was about 30 years ago




Another jeweler told me that a few years back he called some official in charge of this kind of thing to find out what he should do with his cyanide waste. They told him to pour it down the drain. I suppose it is such a relatively small amount that it really doesn't matter.


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## Brandt (Aug 1, 2009)

Before you dispose of it mix some chlorox in to neutralize it. Brandt


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## goldnugget77 (Aug 1, 2009)

Hi Brandt 
How are you
Thanks for your help 
I really appreciate it


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## 4metals (Aug 3, 2009)

Jewelers used bombing solution to polish the gold because it uniformly removes a thin layer of metal from all exposed surfaces. By bombing before polishing the jeweler was able to retain a little more of the customers gold than by polishing alone. 

Classically bombing is a mixture of potassium cyanide and hydrogen peroxide in water and the concentration of cyanide is high.

To recover the gold raise the pH to 12 with caustic soda and sprinkle in fine mesh powdered zinc dust, roughly 2 ounces for every ounce of gold you expect to recover. The gold will drop out pretty quickly and you will see the mud in solution go from brown to grey when it is complete. Filter the solids and you will have a mixture of zinc dust and precipitated gold. Rinse this well and if possible add hot water and boil it for a while to expel any cyanide. You can dissolve the excess zinc using HCl but be careful and do it upwind or in a hood to make sure you don't breathe in any fumes when you acidify what may contain residual cyanide. 

Cyanide is nasty stuff and not easily neutralized without testing equipment. Adding bleach to neutralize is better than nothing but not the best solution. Cyanide is best decomposed in a 2 step process requiring both pH monitoring and ORP monitoring probes. whomever told you it can go down the drain was not helping you much!!!


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## golddie (Aug 4, 2009)

Hi 4metals
Thanks for that valuable info.


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## goldsilverpro (Aug 4, 2009)

Good post, 4metals

That's exactly how I do it except I like 50/50 nitric acid (fastest) or weak sulfuric (least fuming), instead of the HCl, to dissolve the excess zinc. Hot vinegar might even work. Zinc is easy to dissolve.


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## Refiner232121 (Mar 16, 2011)

I was talking to a chain manufacturer and he said he precipitates the gold with zinc powder and he would like to refine his gold afterward.
Here 4metals explains this in a easy to understand way
I dont know if this person uses a ph meter to monitor the solution when cementing but 4 metals says this


> Cyanide is best decomposed in a 2 step process requiring both pH monitoring and ORP monitoring probes


what is ORP monitoring probes 
Also I am assuming that once I wash and boil in hot water to get rid of cyanide I can process it in the usual way
Thanks


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## 4metals (Mar 16, 2011)

The solution which you filter off after the gold is dropped with zinc is loaded with cyanide. This is what you need to treat as it is a hazardous waste.

ORP is the oxidation reduction potential. It measures the ability of a molecule to acquire electrons or be reduced. It is a value measured in volts and every chemical reaction has a specific voltage to indicate the electron transfer has been completed. Cyanide has a very specific ORP value and when it is reached it is an indication that the reaction is complete.


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## Refiner232121 (Mar 16, 2011)

Hi 4metals
Thanks for your help
I really don't know how they dispose of their waist but I will tell them about this
I wont be surprised if they just dump it in the sink because long time ago when I worked in jewelery I don't remember anyone checking the pH level or the 


> specific ORP value


One place didn't even save anything from bombing they just threw it away.


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