# question about potassium gold cyanid



## frank-20011 (Mar 8, 2016)

hello everyone,

my question deals with almolst 100 little plastic bottles from a galvanic shop.

they are emptied by the workers in theyer process but in every bottle there is a little rest of these magic salt, magic to me and toxic too.
these bottles go to the waste, like the much bigger steel drums with NaCN, KaCN and AgCN which go easily into metallic recycling, without any precautions.

back to the plastic bottles, half of them are rinsed with destilled and there is still a rest of these water in em but in the other half of them (they aren't rinsed) you can see clearly the crystals...maybe 50mg or less but 40 times 50mg...
the bottles laying arround for one year or so and now my question is: the little KAg(CN)2 in the rinsewater is clearly hydrolised but the salt in the bottles, it is in contact with humidity of the air and CO2 so is there now Potassium-gold-carbonate in these bottles? Or potassium carbonate and gold cyanide, or cyanate?
How reactive is these salt...i've read KCN is reactive enough in air it smells everytime like almonds cause it reacts with water and CO2 from the air but how reactive is the KAg(CN)2, pure and in water?

Thanks and regards.


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## jeneje (Mar 8, 2016)

If you are smelling "almonds" (without any mounds candy nearby) You may be in the *WRONG* place. If,,, it were me. I would be finding another place to dwell. Another-wards get the hell away from it. :roll: 

Ken


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## Anonymous (Mar 8, 2016)

It's cyanide itself in solution that has the almond smell. Being able to smell that doesn't mean it's gassing off the lethal Hydrogen Cyanide. 

If someone wishes to correct me then feel free but I do agree that not everyone can smell it, I guess I'm one of those that can. GSP/Lou am I wrong in my thinking here? 

Jon


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## Lou (Mar 8, 2016)

Correct. Smelling it does not indicate over exposure. Not everyone can smell it (genetic factor). If you are going to smell it, read the SDS and be sure you know the warning signs. Also, carry a pocket mirror much like what a woman uses for makeup and such--if you see blue in your lips, you are showing signs of overexposure. 


Treat the cyanocomplexes of precious metals the same as you would their alkali cyanide salts--that is, avoid acids, even neutral water. The complexes are quite stable, so don't think it'll just be carbonates of gold.

Lou


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## frank-20011 (Mar 8, 2016)

Hello,

yes, avoid acids!!!

to the smell of HCN-salts:

i've only read! about KCN's smell in germanys "Versuchschemie Forum" that it ever smells weak like almonds because it reacts everytime with "air", means CO2 and H2O. i don't know if that is true!
And i know about genatic factor to be able to smell it.

mhhm, is it as you've said: every metal komplex of CN is stable enough to resist air-humidity, maybe weak acids like H2CO3 (another mate of me said it reacts direct to the carbonate, very, very slowly, without any HCN degassing)?

Regards.


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## upcyclist (Mar 8, 2016)

frank-20011 said:


> to the smell of HCN-salts:
> 
> i've only read! about KCN's smell in germanys "Versuchschemie Forum" that it ever smells weak like almonds because it reacts everytime with "air", means CO2 and H2O. i don't know if that is true!
> And i know about genatic factor to be able to smell it.


IIRC, it's actually the other way around--"bitter almond" smells like cyanide, because that's what gives bitter almonds their characteristic smell.


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## Anonymous (Mar 8, 2016)

upcyclist said:


> frank-20011 said:
> 
> 
> > to the smell of HCN-salts:
> ...



Haha I know and that's the point people miss. don't tell anyone or mass hysteria will occur.


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## frank-20011 (Mar 9, 2016)

hello,

smell of cyanides to and fro but what's about its reactivity in water, in books is written solutions of cyanides should be prepared everytime fresh...what's in the solution of KAg(CN)2 after one year?

regards (sorry for the twotime posting above!)
No problem. I deleted the second post. Dave


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## goldsilverpro (Mar 9, 2016)

PGC is quite soluble in water. I would just rinse out the bottles with water from a squirt bottle. 40 X .05 = 2 grams isn't much though, to go through the procedure needed to recover the gold.


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## frank-20011 (Mar 9, 2016)

Hello,

why not? almost 70% of the salt is gold...take of the little water which is in the rinsed bottles, rinse with these water the other 40 bottles with rest of the solid salt in em, and then let it react with Zn, destroy the ZnCN with bleach or H2O2/copper.

Greetings!


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## nickvc (Mar 9, 2016)

GSP is saying your not going to get rich, his maths is usually spot on and if you only have two grams of gold is it worth the effort! If this material is an ongoing thing simply use boiling water rinse the bottles out and recover when it's worth the extra trouble.


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## upcyclist (Mar 10, 2016)

frank-20011 said:


> why not? almost 70% of the salt is gold...take of the little water which is in the rinsed bottles, rinse with these water the other 40 bottles with rest of the solid salt in em, and then let it react with Zn, destroy the ZnCN with bleach or H2O2/copper.



Say you have a milliliter hanging out in a bottle, and it's 70% gold. If you rinse it out with only 6 mL of water, now you've got 7mL of 10% gold (by volume at least). Now you need to add something basic to keep it pH 10+, to minimize the risk of it acidifying and killing things. Your percentage just went down again. So did your available time, because you had to test the pH to figure out how much NaOH (or whatever) to add, added it, and tested again to make sure it was the correct amount. You haven't even started dropping the gold yet, much less rinsing the precipitate--a lot--to remove the cyanide before you refine it with acid, treating your acid and cyanide waste streams separately, etc.

I'm not saying it's _not_ worth it, just trying to point out why it might turn out that it's not worth it. As with many return-on-investment questions, much of it hinges on whether refining is your primary source of income or not. Even if it's "just a hobby", unless you're independently wealthy, it's probably worth knowing how much it'll cost.


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## frank-20011 (Aug 9, 2016)

Hello,

i've rinsed the bottles two times with two portions of ~50ml of ordinary tap water with a trace of NaOh, store the combined "sollutions" in a little beaker, and add aluminium foil....

after 24h the foil looks a little bit bownish and there are some "scars" and little holes on it too.

i let stay the beaker on a warm place for a few days to reduce the water, make the PGC more concentrated and right: the foil is colored with a "crust" which is more yellow than brown and the holes in the foil get bigger.

Now I am a little bit confused cause, cody's cyanide sollution, made out of gold plated electronic stuff, turns to a nice violett.

you can see it in his video, look at 9:00

https://www.youtube.com/watch?v=HhuwO8AjM7k

my liquid stays almost clear and almost colorless too.

today i'll destroy remaining cyanides with NaCIO.


best regards, frank!


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## anachronism (Aug 9, 2016)

Pure PGC in water is colourless if there are no impurities. 

If your aluminium has discoloured then you have gold forming on it. The holes are where the Al has gone into solution.


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## frank-20011 (Aug 9, 2016)

Hello,

"Pure PGC in water is colourless if there are no impurities."

Yes...i know but why cody has a violett sollution after adding the al-foil and i have ,instead, the gold not colloidal into the sollution (the violett color) but rather on the foil? (after dissolving the foil with NaOH there are little yellow gold flakes)

backt to my "foil": I have dissolved the al with more NaOH, than I've destroyed the cyanide with bleach.
after that i've direct dissolved the gold with AR, filtered the sollution and a clear, yellow liquid was the result.

than denoxxing with sulphamic and: viola-percipatitation with SMBS but the result of the last action was a little bit strange: a first color turns from yellow to violett...after a few minutes some golt settels, fine but after a few minutes more the liquid get more and more muddy and a little bit of a greyish sludge goes down to the bottom of the beaker, like the gold mud but natural not as dense as the gold dust...what could these grey sluge be?

best regards-Frank!


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## frank-20011 (Aug 10, 2016)

Hello,

today ,in the daylight, the sludge is looking more yellow than gray, and a lot of it tend to float in the liquid...i almost think it is sulfur?

strange but not a big problem...i dry the whole sediment of the beaker, the gold with these yellow/grey stuff and try to ignite it to see if it's realy sulfur.

i could not be a metal because its low specific gravity and it's presence in an acídic environment.

has nowbody observe something like that? 

I didn't think the al-foil cause the problem because i am not the only one who use al for the precipitation.

thanks and regards, Frank!


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## goldsilverpro (Aug 11, 2016)

PGC, Potassium Gold Cyanide, KAu(CN)2, is sold in at least 4 ways, usually in packaging containing 1 or 5 tr.ozs. of gold, as metal - always in salt form. I have never seen PGC sold in a dissolved form.

(1) 68.3% gold - pure anhydrous PGC- used in both acidic and cyanide gold plating baths, for make-up and replinishment - no free cyanide.
(2) 68.3% gold - pure PGC plus additives (usually conducting salts and cobalt or nickel sulfate) - used for replinishment of acid baths only - no free cyanide.
(3) 67% gold - pure PGC plus a little added potassium cyanide - only used to makeup or replinish cyanide baths.
(4) 40% gold - Pure PGC plus a lot of added potassium cyanide - only for cyanide baths, mainly for make-up.

(1) and (2), with no free cyanide, are much less dangerous than (3) and (4).

I have done 1000's and 1000's of those bottles. I usually just rinsed them out with a little water from a lab type squirt bottle. Also, I have probably handled 100,000 ounces of PGC in my life and have never smelled the smell of bitter almonds while doing this. I'm pretty sure that bitter almonds is the smell of HCN, the gas that is produced when cyanide, as either a salt or solution, is combined with an acid. 

Except for rare situations, the use of aluminum to drop gold is a very poor choice. It can cause a lot of problems. The best is to use 325 mesh, "zinc dust", which is available on EBay, cheap, the last time I looked. It usually takes from 1 to 2 oz of zinc per oz of gold.


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## frank-20011 (Aug 11, 2016)

Hello,

it was sold as salt, pure and anhydrous (made from Heimerle und Meule)....and i've found these bottles, in the waste of an electroplating shop-almost empty but only almost.

now, one day later, i know the strange yellow sluge in the percipitated gold isn't from the pure Heimerle und Meule PGC.

after glowing the powder it turns brown...like it has to be...a little bit of SO2 fumes comes of but also some others, I won't to smell and inhale these stuff so it's o.k. for me to say it was only SO2 and basta!

I've percipitated the gold from the electroplating shop (only traces from emptied bottles) with some self made PGC.

i have made cyanide like cody and deplate some pins, the resulting PGC was percip. together with the industrial PGC.

i repeated the process yesterdays evening: take some pins, add potassiumcyanide in tap water with a little bit of NaOH and add a few drops of H2O2.
at 50...60°C you can see the plating is dissolving within minutes...or seconds, depending on it's thickness.

after the dissolving of the gold i decanted the clear liquid, tested it with stannous positive for gold and store it over the night.

today i try to reuse the cyanide/PGS-sollution from the process yesterday evening so i pour it over new pins but nothing happened...i decide to warm it up in a waterbath and add a little bit H2O2, istantly the liquid get yellowish-cloudy-flocculent and a new test with stannous was negativ.

why the former positiv cyanide sollution is negative after ~20hrs?

there wasn't an reducing agent, it's alkaline....?

i will use zinc powder in future, i have only coarser zinc filings and so i decide to use the Al....nice optic: when the gold is falling of from the dissolving foil it forms little flakes, one side is brown/yellow and the other, the side which is sticking on the al, is shiny.


regards, frank!


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## anachronism (Aug 11, 2016)

There's an awful lot more to making a cyanide leach than meets the eye. It goes way beyond Cody's videos. What are you using to get SO2 gas? Are you using SMB to precipitate?

What was your cyanide strength in grammes per litre? What was your H2O2 percentage per litre? Take your base H2O2 strength and calculate.

What was your estimated gold in the batch and your overall volume? Also PGC is already a gold/cyanide complex so it won't be dissolving any more gold without free cyanide to do so.


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## Topher_osAUrus (Aug 11, 2016)

You are testing CN with stannous?!? :shock:


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## frank-20011 (Aug 11, 2016)

Hello,

"What are you using to get SO2 gas? Are you using SMB to precipitate?"

Yes, after precipitation and after destroying the cyanide i use AR...than filtering and than SMB, not only gold settles but also a yellow sludge...i dry the sludge/gold and glow it, i'am only speaking about ~500mg


about my process: i work as crude as cody, i know nothing about the real cyanide level in my "cyanide" and so i can't say anything about it's concentration in my sollution and so on.

it "seems" to work fine and the alternative is the sulfuric acid deplating cell...

"You are testing CN with stannous"

yeees... a half drop of the sollution and a half drop of the acidic stannous sollution on a paper towel...
hokes say i should take 5ml of suspectet liquid and add HCL to wait for CN and "stand near a window"...that isn't viable to me!

thanks and regards!


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## anachronism (Aug 11, 2016)

goldsilverpro said:


> Also, I have probably handled 100,000 ounces of PGC in my life and have never smelled the smell of bitter almonds while doing this. I'm pretty sure that bitter almonds is the smell of HCN, the gas that is produced when cyanide, as either a salt or solution, is combined with an acid.



Hi Chris

The bitter almond smell comes even when working with a pH 13 solution. Are you sure that maybe you're just one of the many people who cannot smell cyanide?


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## goldsilverpro (Aug 11, 2016)

anachronism said:


> goldsilverpro said:
> 
> 
> > Also, I have probably handled 100,000 ounces of PGC in my life and have never smelled the smell of bitter almonds while doing this. I'm pretty sure that bitter almonds is the smell of HCN, the gas that is produced when cyanide, as either a salt or solution, is combined with an acid.
> ...


I can smell cyanide solutions. They supposedly have a straw-like smell and that's sort of what I think they smell like. Over a 4 year period in the early 70's, I visited several hundred plating shops. Every one I remember had huge vats of cyanide plating solutions. They usually contained at least 1/4 pound of CN/gallon and some held thousands of gallons. Here again, no bitter almond smell - strong straw like smell always. Very distinctive.

In the Air Force, I taught a 40 hour course, once a month, on Chemical, Biological, and Nuclear Weaponry. The school I attended for this had what they called a "sniff kit", to familiarize the students with the smells of the different chemical agents. This consisted of very large test tubes, each with a solution or substance in them, sealed with a stopper. One contained a substance that emitted HCN. To use these, one removed the stopper and sniffed it. You didn't sniff the mouth of the test tube. I seem to remember the bitter almond smell distinctly.


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## anachronism (Aug 11, 2016)

Ahhhhhhhh now that makes sense! 

That description of the smells is much clearer and makes a lot more sense if you pardon the pun. 

I'm confusing the strong straw like smell with bitter almonds. Learned something valuable here, my thanks.


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## frank-20011 (Aug 11, 2016)

hello,

i didn't ask for any almond smell....i've only wrote about a strange yellow sudge which was formed within my gold percipitation.

i've glowed the gold percipitate together with the yellow slurry and it smells like SO2, mainly but also a little bit like Cl and ...?... but no problem about that, the problem was the sludge itself....these and my improvisitional cyanide "process".

how i should test cyanide sollutions for gold?

best regards, frank!


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## goldsilverpro (Aug 11, 2016)

What in the hell does "glowed" mean?

Gold will form a yellow compound, AuCN, gold cyanide, insoluble in acid, when a PGC solution is acidified below a pH of about 3.5, if I remember right. We used to see it occasionally in inefficient acid (pH 4.3 optimum) gold plating solutions whose pH had been allowed to drop too far. Inefficiency in the amount of gold deposited per amp-minute can cause a pH drop.


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## frank-20011 (Aug 11, 2016)

hello,

sorry for my horrible english but i am here in an i-cafe and so i can't use spelling check....only my lousy school english!

"glowed" means: i've heated it on a steel sheet with propane burner from underneath until it glowes...after that it looks like precipitated gold should looks: red-brownisch....not yellow-greyish as it looks before!

best regards!


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## FrugalRefiner (Aug 11, 2016)

Here, we usually call it incinerating. In college, we referred to it as igniting.

Dave


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## frank-20011 (Aug 15, 2016)

Hello,

i have more questions about...let us call it "codys cyanide": after the pins stand over night in the diluted cyanide (with or without H2O2) sollution the liquid get muddy-white (the right test tube) and than, if i add few drops of H2O2-3% the color gets from white to yellow (test tube in the middle) with a few more drops of peroxyde it gets bown (left tube)





is this the result off dissolved iron ions?

the 2nd thing is the question for a gold test in an alkaline cyanide sollution.

is my test possible? i add stannous in HCL to a single drop of gold-cyanide, made it acidic and the gold drops out by the stannous?


best regards!


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## frank-20011 (Aug 15, 2016)

Hello,

on an other place in the forum i have found GSP's statement to a cyanide test:

"There's a go-no go method in the Hoke book that takes a small amount of sample, acidifies it with HCl (under the hood), and then tests it with stannous chloride - I've never tried this. In my experience, though,"

and this is almost the test i've used, only in my stannous is so much HCl that i didn't have to add extra HCl!

i didn't found that in Hokes, only that one I've described above.

best regards!


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