Is this cyanide?

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Ignatz61

Well-known member
Joined
Jan 2, 2008
Messages
108
Location
NY
I have aquired some sludge from under a Gold plating machine used in plating circuit boards a long time ago. It has been sitting for about 10 years.
There are green crystals and brown muck. The liquid is also brown.
How do I check to see if it is cyanide?
If it is cyanide how do I kill it?
I carefully mixed a small amount with some HCL/Cl in a fume hood. It tested positive for gold but the purple color came on slow. It took almost 10 mins to show purple.
Any help?
 
Most cyanide testing today is done by test kits. There is an older classical method of indicating cyanide resulting in the formation of Prussian Blue. Take a sample of the material in question and dissolve it in warm water, filter it to eliminate any interferences. If there is cyanide it will have dissolved in the warm water. Now add some Iron (II) sulfate to the solution and acidify it with any mineral acid, and if there is cyanide in solution it will form iron ferrocyanide which is Prussian blue. It is an un-mistakable blue color.

This is a test to be performed on a small sample and under a hood, after all you are acidifying a suspected cyanide solution.

If it turns out to be cyanide it can be dissolved and neutralized with bleach. A complicated process which will require both a pH meter and an ORP meter to perform properly. I would try roasting the dried sample of the sludge. Cyanide decomposes in the roasting process and you can crush up the dry product of the roasting and digest it in a small amount of aqua regia. Then test it for gold with stannous chloride. Try this on a small sample in a good hood before processing the entire lot.

I have found many piles of crystallized crud on plating shop floors. Your pile, due to where it was found, may be gold or it may not. Chances are other metals are present also. Be careful, test carefully and on small samples, and good luck.
 
Thanks 4metals,

I have been very carefull about the fumes, and only worked in a hood on small samples.(Acid + cyanide = gas chamber gas) I have 3 spackle buckets each about half full of liquid and sludge. They came from two plastic tanks that had a pump, a heater and some plastic hoses. I think one was more of a rinse and the other the plating solution. I believe plating solutions work best when heated so the heater in the tanks I think was a good sign.

When I tested them at the site one showed a much darker indication with stannous chloride, But both did show positive for gold. As did residue on and around the equipment in that area.

Now the trick is finding out how much gold is in the mix, about a quarter of it is thick muck that I could dry and roast but there is maybe 7 gallons of brown liquid.
Not having much of a chemistry background I am treading slow and carefully. You said I would need a ph and orp tester? Can you layout the procedure?
Could I add zinc to drop all metals, then roast the solids and separate as if it where bench sweeps?
 
This is where you can find the procedure for breaking down cyanide.
http://goldrefiningforum.com/phpBB3/viewforum.php?f=37

Your suggestion of using zinc has potential, first I would separate the solids by filtering, those can be roasted separately and tested as we mentioned. The liquor can be treated by dropping all of the metals with zinc, then filter the solids dry and roast them, then HCl to get rid of excess zinc followed by aqua regia on the residues. Finally the liquid from the zinc out can be treated with bleach and and left out to be oxidized by the sun in an open bucket. That will kill a moderate amount of cyanide, if the cyanide concentration is high (as old plating solutions usually were) evaporate it to a solid and roast it. Test a sample for gold before you get rid of it, can't be too careful at $1000 an ounce gold!
 
Ok,
I have processed some of the residue from a plating tank. It tests positve with stannous chloride after HCL/CL. But the purple color took a long time to show. Like 10 mins.
Added SMB to liquid (after hcl/cl soak) and it turned canary yellow and dropped a yellow precipitate. I don' get it? The only metals that should be present are Nickel, Copper, Gold or lead. Can any of these cause the yellow color?
 
Try filtering off the yellow precipitate and checking to see if it is soluble in HCl. If it is it's most likely copper chloride. How much of the roasted powder did you digest in how much acid? How much SMB did you add? Was the roasted material heavy (dense) or light and fluffy?
 
The yellow precipitate might be gold cyanide (AuCN). It forms when KAu(CN)2 solutions are acidified. It is only soluble in cyanide or ammonia. I don't remember having ever tried to recover gold from an ammoniacal solution.

Were I you, I wouldn't acidify any more of the material. I think I would take a small sample of the original material and try to get it in solution by adding a little water and heating it. Then check the pH. If it's alkaline, it could very well be a cyanide solution. I would then raise the pH to 12 with sodium hydroxide and try to drop out the gold (or, ?) with powdered zinc. Filter, rinse well, and then dissolve the excess zinc in nitric acid (under the hood). If you end up with a brown powder, it is probably gold.
 
I haven't roasted any material yet. The beaker is brown residue I added HCL/CL to (Under the hood) and It tested Positive for Gold. I tried to drop the gold with SMB and got the yellow precipate you see in the Picture. Because the tanks and equipment were all part of a gold plating operation I suspect Cyanide is in the mix. Thus the reason for treading slowly and carefully.

GSP-If my precip. is gold cyanide, Can I pour it into the other 7 gallons to redissolve?

Or does anyone have the procedure for recovering the gold from ammonia solution?
 
You put it in acid without roasting it! Why did you bother asking what to do? Cyanide is nasty stuff, it can kill you. The reason behind the suggestion to roast it is roasting will thermally decompose the cyanide.

Now I understand why others refuse to talk about cyanide. There are too many people with no chemical background here who play with chemicals and can't follow advice.

I'm converted, no more cyanide advice!
 
4metals,
I am aware of the danger involved in acidifying cyanide. I am sorry if I did not spell out my precautions more completly. I am working with a small quantity of material, It was not part of the 7 gallons of material I asked you about that I pretty much know has cyanide in it, but, because it was found in the same area as the plating stuff I proceeded carefully, It was dried out ( resembling gold precipt. from AuCl). So I put a small amount in a beaker in a fume hood ( using a quality resperator), added Cl and HCL , I let it sit overnight with the hood running. I added some SMB and ...Yellow. In retrospect, your right I probably should have roasted first even though it was different from the material that is very suspect for cyanide.

I did mention in my earlier post that Acid and cyanide makes the gas they use in the gas chamber. I did not want anyone to think I was cavelier about the dangers of messing with cyanide.

I am sorry if I caused undue concern. I am proceeding slowly and carefully and very much appreciate all the help. I am filtering the solids that I can out of the liquids and will roast them. (Rubber gloves, face shield, vetilation.) The liquid I will add water and warm, check/adjust ph and try to drop the gold with zinc as we discussed.
 
This is getting confusing. You have 2 different things going on and, at this point, no one really knows what is in either of them. I can think of lots of possibilities and not all of them involve gold. Until you find out, do experiments in very small quantities. Try what 4metals suggested and what I suggested, on small samples. Don't worry about blending things together yet and don't treat the entire 7 gallons until you have a process. Report back on your findings.
 
OK,
(I added some of the sloution to warm water added ferric sulfate then HCL, No Prussian blue color. But I am still proceeding as if cyanide.)

I have roasted the solid material (Crystals and brown slime) at 900 F for 2 hours. In a well vented fume hood, I dissolved 2 teaspoons of the powder (hard sand like powder) in a beaker with HCL. I got very green solution and some undissolved powder, tested the liquid for gold- Negative. So I decanted and dissolved the remaining solids in HCL/Cl. Liquid color now is yellow. Test for gold with stannous - Positive. (the purple color took 5 mins to show).
Let sit overnight, Added SMB and fine white powder settled. Test with stannous showed more concentrated (Darker purple) gold.
This is where I am at now. So...
Is the white powder Some form of copper? I am sure there is allot of copper in this stuff. I decanted and hit the liquid with SMB again. More white powder, liquid still shows purple with stannous chloride.
Should I keep doing this or is it possible there is something in there that is preventing the gold from dropping?
Should I Use Zinc now and refine again or will I just wind up with the same contaminates?
 
what I am bit confused?
copper will not precipitate before gold,
I would first determine which ion (acid or base portion)the material, metal-salts or solution was, this should not be hard testing small samples for cyanide, sulfate's, chloride's, and then if possible wich metal involved.
but since you neutralized and roasted (at a temperature 900 deg,high enough and two hours seems good for most sulfate salts) I would have had used a torch over powders till red hot , as salt crystals can shield their inner part (crystal) from heat. when melting metal-salts it is ammazing how much acid can evolve from them, higher the temperature the more acidic solution develops till all is driven off in gas, the negative ions should have been driven off in fumes.

since you then used HCl/ bleach if you then concentrated, or boiled (I see no mention of it).
the HCl/Cl will make table salts in solution and concentrated will precitate NaCL, this salt (or any concentrated salts in solutions) drag metals with them (I think they form crystals with these other salts), decant your yeller solution and test this white powders,

I would add hot water first to see if they dissolve, then HNO3 to check for any silver, or lead, dilute & add HCl, you can keep going till you know exactly what you have.
what confuses me is why would anybody in his right mind process a metal, salts solutions or perform any chemical expieriment etcetera, before they found out what it was they are dealing with, there are so many deadly reactions, or explosive reactions that are possible with dealing with chemistry or these metals in solutions, or powders, and testing is so easy , and finding information of how to test is also so easy , so much information on this forum, with people willing to help and with the intranet a person can find any information, chemistry books can be downloaded etcetera, with all this information avalable that can keep us, and others safe, and eliminate the guessing game,
Ignatz61 you may well know what you are doing here, more than I do. from reading this post, I have not dealt with cyanide, but if I did believe me I would do alot of studying first, and If I deal with any Unknown ore, metal, salt, or solution, I would make it my first priority to find out the very best I could what it was,
as other Wise men said here (IN SMALL PORTIONS) so that conditions or chemistry does not get out of hand.
as one man with knowledege keeps saying why run blind (you will bump into trees in this forest), w these metals are not worth our safty. and our health can cost us more than we can get from them.
do not take this post as anything but my rambling on and wanting to help.
 
Everyone here has been very helpful and I have learned much from this forum. I don't know if I have not been clear in my quandry here.

I obtained several containers of material from a defunct manufacturing plant. Some are dry powder in unmarked tubs, some wet sludge from under a machine that had labels on the controls like, " Nickel plate", "rinse" and "gold plate", "rinse". So I tested for gold and got positive readings.

There is nothing else to give clues as to what is in the buckets.

SO!

I am assuming cyanide (most conservative) even though all but one bucket have acidic sludge, One has ph 7-8 and none show blue when following 4 metals advice for testing for cyanide, Still, I am working with teaspoon size samples in a well made fume hood, trying to figure this out.

I have been reading and researching and experimenting to try to learn and unlock the gold. I don't know what the salt is that is precipitating, but based on where it came from I suspect there is Nickel, copper, gold, and / or lead (soldering machine) in any or all of the solutions. All I know is this.
1. I roasted the sludge from Machine #1
2. I put 2 teaspoons in a beaker, added about 200 ml HCL
3. Tested Liquid, NO gold, So Decanted and added another 200ml HCL and about 50 ml Cl to the undissolved powder
4. Tested liquid- slow but positive for gold (stannous Chloride)
5. Added SMB
6. White (salt?)Precip. Tested liquid for gold fast and dark positive.
But No gold precip, YET Added more SMB twice same white precip.

Zinc takes down the gold but I don't know what else is coming with it. redissovle and re-refine same white precip.

I thought this would be an interesting challenge for this forum considering the brain power and collective experience here.
But I seem to be causing much concern and panic about trying to tackle this without much experience with cyanide, despite mentioning often that I am aware of the gas that acid and cyanide makes, That I am using small samples in a fume hood. and I am (or was) asking questions when things did not go as I thoght they should.

Perhaps 4-metals is right, this is not the place to talk about cyanide procedures.


Iam sorry if this sounds negetive I enjoy this forum very much.
 
sounds like you have a handle on it, I was not trying to discourage you, just it should be fairly easy to determind whether suspect solution is acid or base, a cyanide, sulfate, or chloride.
and it sounds like you are taking precaution's. I missunderstood and thought you were doing large volumes seeing the beaker full. not having expierience with cyanide myself maybe I am just leaning toward caution. this is a gas that kills, there are so many people who will try and do things without understanding,

I in no way was saying you were Ignatzi61, but we sure don't want to loose any of our fellow forum members, so please be careful,
have you tested the white salt for silver, lead, cloride's of these are insoluble in water, and can be slightly soluble in acid solution. mercury chloride also insoluble. sodium chloride, could have formed from muratic and household bleach.
if you have a gold in solution, and a white salt it is a not base metals like copper or above, besides silver lead or mercury, NaCl , (or a salt of some other nature, but that would suggest roasting process was incomplete).

from the picture of the beaker it looks concentrated, which very could mean table salt NaCl and possibly silver, does adding three times the volume of water and some salt. letting settle over night clear solution and precipitate white cottage cheese powder's (silver) ?
 
Thanks Butcher,

I just tested the salt and it is very soluable in water. 3 volumes of water and the salt is gone.
Stannous test is more brown than purple, diluting the solution lightened the test color. Before it was that blackish purple that high gold concentrations would show. Now it has lightened to a dark brown maybe a hint of purple. Maybe less gold than I hoped. But if there is not much gold why the yellow solution? When I added HCL to the roasted powder it turned green. I expected that due to copper from the circuit boards, But after decanting and adding HCL/Cl to the powder It turned yellow like AuCl. What else would turn yellow?

I may just zinc the solution, and melt the powder (after washing) letting flux do some of the cleanup. I need to find out how much gold (if any)is in the 2 teaspoons and whether it is worth dealing with the rest.
 
the green powder most likely was copper , or nickel.
and adding water to solution seems it was a table salt from your acids, is the solution clear? or turbid looking, did it precipitate any white silver? it will not hurt to add some table salt, or HCl to your solution to see if any silver will precipitate, it will make white cloud then form cottage cheese, and will take a while to settle if silver is in there, if so add salt till no more cottage cheese forms, let sit over night, decant solution, filter and treat with sodium sulfite or sodium metabisulfite, ferrous sulfate, or the precipitant you use for gold.

if solution is yellow you should not have enough copper to give you that much trouble, once your gold has precipitated wash and refine it again for purity.
 
The solution after adding water and dissolving the salt was turbid slightly brownish. I am letting it settle to see if I get any brown powder.
 

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