# cyanide leach! cant get 99% Gold recovery



## bee (May 16, 2013)

recently i used the cyanide leach on gold plated pins the method is exactly described by GSP i set the ph to 12 and then add ZINC powder stir time by time after 24 hours i catch the black gold dust with zinc dust. problem is 
on both two experiment its need too much zinc powder.
first batch of 13LB rams fingers i add 100 gram zinc powder and after 9 hours i got only 12 gram gold then add another 100 grams stir time by time after 24 hours get 6 grams. now add again 100 grams and stir 24 hours and get another 6 gram.
i donot have source of zinc powder so you cant imagine its a hard working i rub the zinc metal with a sharp rubbing tool i donot know the English name but i get 100 grams zinc powder into 9 hours. as English is not my first language.
so can i use zinc oxide instead of zinc powder?
why its taking so much zinc powder and giving only few grams of gold?
now i am tired and left the solution alone but i am 100% sure there is much gold left what is brown or gray fog which is so fluffy and fly all around when you add the zinc powder?
add about 300grams of zinc powder now how much its need more?
can GSP as he is expert enlighten me what is going wrong as he also add the the zinc powder i make the ph 12 with NAOH and try to follow him read all posts through google through this awesome forum but i am really confused the the liquid color is still brown type, the precipitate is black also the last two addition of 200 grams zinc powder given me only 12 grams gold which you can consider how hard is this when you add 50/50 HNO3 and yes i have very good hood setup and have chemistry back ground .also kindly do suggest me is zinc oxide can be used other than zinc powder?
thanks
bee


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## goldsilverpro (May 17, 2013)

bee,

My guess is that the zinc is the problem. In my posts on the subject, I think I always said to use 325 mesh "zinc dust" (only by that name). In my experience, the gold tends to coat the zinc particles and this blocks the interior zinc from reacting. With coarse zinc, this can result in great inefficiency. The zinc powder you're producing is surely much, much coarser than 325 mesh (which is about 44 microns - .0017"). For example, if the powder you're producing is, say, 8 times larger (.013") than 325 mesh, the individual particles would weigh 500 times more. 

Zinc dust, 325 mesh, is available on eBay, for about $4-$6/pound. The zinc dust tends to clump with moisture so run it through a fine sieve before using.

There is a zinc powder commonly available that contains a silica anti-clumping agent called Cab-O-Sil. It's not called "zinc dust". Most I've seen was 200 mesh. The silica tracks through the process and makes the gold refining more difficult. Don't buy any zinc powder with Cab-O-Sil in it.

Instead of zinc, I've first filtered the solution and then had good luck plating the gold out. Just rig up 2 electrodes made from stainless sheet. For a 5 gallon bucket, I would make the electrodes about 6" x 6" and use about 3 to 4 amps DC across them. If you clean the stainless before using, don't use anything even mildly abrasive. The passivated surface might be damaged and the gold will then stick to the cathode and be difficult to remove. Some of the plated gold might fall off the cathode and be on the bottom.


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## samuel-a (May 17, 2013)

Instead of Zn dust, Steel wool is very cheap and very affective.


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## goldsilverpro (May 17, 2013)

samuel-a said:


> Instead of Zn dust, Steel wool is very cheap and very affective.


Have you ever tried this, Sam? I haven't, but I would question whether it would work. When I strip, I tumble it in a steel cement mixer and have NEVER had any gold deposit on the steel. The solution I use has a lot of cyanide and peroxide in it. In order to deposit gold on the steel wool, some of the steel wool would have to dissolve. I don't think that will happen by immersion in a simple cyanide solution. There are electrolytic processes that utilize steel wool cathodes to remove gold from cyanide but I've never seen one by simple immersion.

https://www.google.com/search?q=steel+wool+gold+cyanide&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-USfficial&client=firefox-a


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## samuel-a (May 17, 2013)

Yes Chris

The cementation actually looks more like plating. It does take longer though, it took about 48 hours until the iron wire structure broke down and leave small wirs of gold.
I have pictures somewhere, i'll try to find them.

I believe the steel of cement mixer is different from the steel wool.


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## samuel-a (May 17, 2013)

Found it in my phone.
The first one is the gold wires left after all the wool was gone.
The second picture is of the same solution but with Zinc ribbons cementing the gold.


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## bee (May 18, 2013)

thanks so much Chris and Sam,
i think i should have use the electrolyte to plate out the gold.
Chris do i follow the same procedure like brought PH to 12 by NAOH and then use stainless steel two sheets?
what type of stainless steel sheet 304 or 316?
what is recommended thickness of sheet?
i ,ll use 12 vot 3 or 4 dc is this fast? i mean how much time it ,ll take to plate out a 5 gallon batch and how do i know the batch is empty and there is no gold left?
Sam kindly do give me a little more information about using the steel wool.
and yes you are right the problem is really Zinc because my zinc powder is about 200 mesh.
i am not able to use ebay as i am not into US i am far far away and if i try to buy zinc dust through ebay i ,ll face too much shipping cost.
thanks so much guys.
bee


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## samuel-a (May 26, 2013)

I used same process as with zinc.
Add NaOH to ensure solution is basic and add steel wool.


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## Gratilla (May 27, 2013)

For cyanidation to work, oxygen is necessary for the chemical process and air or oxygen is typically bubbled through the cyanidation tanks.

However ... cementation is a (partial) reduction process and is hindered by oxygen.

Cyanidation projects that use cementation (usually zinc) typically use a vacuum pump to extract oxygen from the pregnant cyanide solution prior to adding the zinc.


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## bee (May 28, 2013)

How to vacuum pump to extract oxygen from the pregnant cyanide solution?
thanks
bee


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## samuel-a (May 28, 2013)

Bee

Chemistry 101, if you reduce the pressure in the solution tank you will change the equilibrium.
Dissolved gases will strive to go back to the gas phase.

You could find more info on google using "Le Chatelier's principle".


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## Gratilla (May 28, 2013)

You can also force out the oxygen (and other dissolved gases) by raising the temperature of the liquid (ie the solubility of gases in water usually decreases with increase in temperature). But the last time I looked at the solubility curve for oxygen in water, it still showed a decent amount of dissolved oxygen at 100 deg C (ie boiling point).

So a vacuum pump is the way to go.


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## bee (May 30, 2013)

thanks guys.
sam this steel wool is easily available kindly correct me that this is working fine.
http://en.wikipedia.org/wiki/Steel_wool
thanks


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## samuel-a (May 30, 2013)

Yes, plain steel wool.
Gentle heating, 40-50 °C will make things go faster of course.


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## bee (May 30, 2013)

thanks sam i ,ll use and post the results
bee


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## goldsilverpro (Jun 1, 2013)

Sam,

Good job. It certainly surprised me that the steel wool worked. If you don't mind, I have a few questions. What cyanide formula did you originally use? What was the source of the gold that was dissolved? Is all of the steel wool inside the gold dissolved? How did you test the solution to determine if all the gold was out?


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## samuel-a (Jun 11, 2013)

Chris,

Sorry, i forgot to answer.
The starting material was solid crystals that were precipitated in an plating baths. I do not know the exact composition of the electrolyte nor the composition of the solids.
I have dissolved the crystals with dilute warm NaOH solution and placed the wool inside. Kept it warm for several hours.
The iron/steel from first addition of wool had been completely dissolved and the wire structure disintegrated. To test complete dissolution i turnd to the oldest trick - a magnet.
Then, the gold "wires" were filtered and new wool was added. The proces repeted two more times. The third time, the wire was coated with gold but magnetic after sveral days in solution, hinting there was no more cementation.


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## loghman1351 (Jul 28, 2013)

What color is the deposition of gold in cyanide?
I deposited with aluminum foil.
White is the color of the precipitate.
Why
Sediment color is important?
Be black, or color does not matter deposition?


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## loghman1351 (Jul 28, 2013)

I did 300 kg soil with cyanide. Poured sodium hydroxide solution, filtered
Aluminum foil and placed in a solution. The 0.5-inch foil
After 2 days, the white precipitate.
May be precipitated white gold?


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## chlaurite (Jul 28, 2013)

Naive question...

I understand that, for most of the recoveries we do, we tend to use HCl/Cl because it counts as fairly safe (where "safe" means "causes instant burns on contact" as opposed to "one good whiff will destroy your lungs :shock: ); and AR works a good bit easier, though a lot more dangerous and (for most of us) both more expensive and harder to get the reagents.

But for what purposes would we *ever* intentionally choose cyanide over something safer? This one seems almost like a no-brainer.

/ Not even _remotely_ interesting in trying it, only wondering out of intellectual curiosity.


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## Geo (Jul 28, 2013)

chlaurite said:


> Naive question...
> 
> I understand that, for most of the recoveries we do, we tend to use HCl/Cl because it counts as fairly safe (where "safe" means "causes instant burns on contact" as opposed to "one good whiff will destroy your lungs :shock: ); and AR works a good bit easier, though a lot more dangerous and (for most of us) both more expensive and harder to get the reagents.
> 
> ...



cyanide leeching will remove PM's from visible areas on electronics without removing gold plated items from the board. gold plating is removed without degrading the base metal substrate. cyanide leaching is used in mining today to remove PM's in mining operations all over the world as it is inexpensive and has a very good reclamation percentage compared to other leaches where base metals can effect the outcome.


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## loghman1351 (Jul 29, 2013)

Thank
Please give information on gold electrode in a solution of cyanide


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## chlaurite (Jul 29, 2013)

loghman1351 said:


> Thank
> Please give information on gold electrode in a solution of cyanide


Look, I don't mean to make fun of your English skills. Honestly, you know English better than I know any other language!  

But Cyanide will KILL (matar, tuer, vras, doodmaak, öldürmək, убивать, dræbe, 杀, להרוג ,قتل) you dead, dead, *dead*, if you don't know exactly how to use it correctly and safely.

_Please_ don't try to scrape together a crude understanding of using cyanide from an English forum unless you have a fluent grasp of English.


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## Gratilla (Jul 29, 2013)

Guys, I think there is just a little bit too much uninformed emotionalism (err, hysteria) surrounding cyanide.

Cyanide, just like many of the other chemicals that we deal with, has its own pros, cons, etc. And it's up to us to become properly informed as to appropriate safety issues.

Here's what Doc Williams has to say about cyanide:

http://webpages.charter.net/kwilliams00/bcftp/docs/cyanide.htm

I for one would much prefer to deal with a cyanide spill than say, hydrofluoric acid or even concentrated AR. Although cyanide reacts with hemoglobin, it is metabolized (ie broken down) by the body and you can recover from minor exposure (although I'm NOT recommending this), in contract to say carbon monoxide, etc.

Be informed, be safe.


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## solar_plasma (Jul 30, 2013)

@Gratilla

Looking at the LC50 of cyanide gas and its fast effect, it is nothing I want to have around me. But you are right, some other materials should scare people much more then they actually do. A burning bed produces HCN. CO kills without you will smell or taste or even feel it and is cumulative under incorporation, too. H2S's toxicity is similar to HCN, but it smells so bad, that intoxications seldomly occur.

But when such materials could be present, you will use some kind of warning method. You have a smoke alarm in your bedroom. A CO-alarm beside your chimney, a gas alarm beside your gas installation. Earlier candles and birds were use in mines. If someone uses cyanide professionally he will have some kind of instrument to measure HCN, a multi-warn, a PID or an IMS or whatever. Those you will not get in your local DIY warehouse and most people, who could get attracted by cyanide, because it is "cheap" will probably not use some thousands or ten thousands of dollars to búy professionall measuring equipment for a hobby.

Yes, AR or ACl are truely dangerous, too, but you see, smell and feel the danger, you have more time to react and it can be handled. I am sure, KCN can be handled, too, but only one little mistake would have much more serious consequences.

I like to READ about the process, because the chemistry is interesting and I'd like to understand it, though I don't even dream of using it. Something I never found an answer for: *Why isn't gold cementing back, when leached with cyanide? *Everyone who is using cyanide surely knows its chemistry and can answer this!


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## butcher (Jul 30, 2013)

Gratilla,
I agree with you to an extent, many things nowadays are vilified, and many times misunderstood, sometimes the dangers almost seem exaggerated, But then again many times these dangers are very real, and depending on circumstance the dangers may even be underestimated, if a person has a good understanding, Knowledge, skills, and safe working practices he can work with very dangerous materials or do very dangerous things relatively safely, But then again there are always those unexpected incidents, mistakes, human error, or just accidents, and even the well trained professional is killed...

With the people who read just enough to get themselves hurt, thinking they can do this thing that seems so simple to them (not knowing what it really takes or involves, or its dangers)... this forums unwritten policy's of not promoting the use of cyanide. And warning of the dangers, I feel is a good policy, ( I also notice here the most warnings are given by those who do have a good understanding and have used cyanide), just think how many people would mix up a batch with little or no understanding, and would poison themselves or others, thinking they could do something they seen in a you tube video, or something they read in one or two posts on a internet forum, just wanting to get some quick gold without spending the needed time to get the education before trying something stupid.


Be informed, and be safe. Problem is many people will not be informed or be safe.
No doubt about it working with cyanide can be deadly, even for a professional who is well trained.


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## Gratilla (Jul 30, 2013)

solar_plasma said:


> *Why isn't gold cementing back, when leached with cyanide? *



But it is! Although I'm (peripherally) involved with a cyanidation project, we use carbon and not cementation.

Some large operations still use zinc cementation. The main reason that small operators don't have much luck with cementation and discard it is because IMO they don't appreciate/understand the basics and don't use it properly. ie high surface area powder or mesh, (vacuum pump) extract oxygen from pregnant leach first, etc, etc.

The future I believe will be solvent extraction using PH-modified organic solvents.

Butcher, re safety procedures for cyanide: Some months ago I was surprised (maybe even shocked) to hear that the main safety advice for the local artisanals using cyanide was, "If feeling faint or woozy, retreat from cyanidation tank and lie down until recovered." Talk about being cavalier.


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## freechemist (Jul 31, 2013)

Gold Silver Pro writes:


> My guess is that the zinc is the problem......


It's not the zinc alone, it's the zinc cyanide formed as well. Zinc cyanide is practically insoluble in water, and forms a protecting cover on the zinc-metal used to cement gold. Thus, the reaction *Zn(metal) + 2 [Au(CN)2]- => 2 Au(metal) + Zn(CN)2 + 2 CN-* becomes very slow, or even seems to stop. In my practice a good measure against this passivation of metallic zinc was, to dissolve enough ammonium chloride in the leach-solution to be treated with zinc-powder, before it's addition (10 - 50 g NH4Cl per liter).
Zinc cyanide dissolves in aqueous ammonia, forming soluble zinc-ammine complexes: *Zn(CN)2 + 4 NH3 ==> [Zn(NH3)4]2+ + 2 CN-*. The ammonium-ion, NH4+ is a weak acid, and reacts with free cyanide in solution to hydrocyanic acid, HCN, and aqueous ammonia: *NH4+ + CN- <==> NH3 + HCN* The acid strengths of NH4+ and HCN are about equal, and so neither all added ammonium-cations are deprotonated, nor all free cyanide is protonated to hydrocyanic acid.


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## Gratilla (Aug 3, 2013)

I somehow suspect that cyanide is about to make a comeback:

http://uk.news.yahoo.com/texas-running-lethal-execution-drug-113720871.html#Jb9KegJ


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## butcher (Aug 3, 2013)

Plenty of rope in Texas, just Hang them.


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## kjavanb123 (Jun 5, 2014)

Samuel,

I dropped in a steel wool as you did in this threat, into a cyanide solution, here is what it looks like after 24 hrs, please advise how long more does it need to stay?




Thanks
Kevin


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## dannlee (Jun 5, 2014)

Kitchen pot and pan scrubbers usually are stainless steel; the piece shown surely resembles the bright nickel of a pan scrubber...

Steel wool is much cheaper and easily rusted - a common example is pictured:


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## Lou (Jun 5, 2014)

Steel wool is very effective when used electrolytically. 

The gold is substantially out of solution (low tens of ppms, then onto resin) when current density drops and much more gas is produced.


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## kjavanb123 (Jun 6, 2014)

Dannlee,

Thanks for your info that certainly helped me to use the right materials, plus that explained why I didnt get any plating on this material I used.

Lou,
Could you please elaborate on electrolyical parameters? I read in a post by GSP, he used 6x6 inches stainless steel plates, submerged into 5 gallon bucket filled with cyanide solution connected to 3-4V DC current, is that what you meant? Instead of using cathode use steel wool shown by dannlee?

Thanks and regards
Kevin


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## Lou (Jun 6, 2014)

Yes, use steel wool. Everything else the same. Good stirring is important, heat helps, amongst other key points.

I suppose I could tell you how to do this very well, but I really don't like to see people use CN here on the forum and would rather people not get involved with it. Safety and responsibility are paramount, and this is one of those topics (Pt handling being the other) where if you have to ask, you ought to reconsider or hire someone who knows.

Sorry, but my memory is long in your case kj.


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## kjavanb123 (Jun 7, 2014)

Lou,

Thanks for confirming the steel wool concept. As far as hiring someone to tell me how to electroplating gold on ss cathodes, I have no problems but no one has ever pmed me with an agreement even I asked few times . But I thought this was a forum where people share their knowledge.

I cant find the steel wool pictured here so either havr to ball mill my existing troubled zinc powder or find scrap steel wools made in craftiny shops.

Regards
Kevin


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## Lou (Jun 7, 2014)

Any magnetic steel wool that burns with a battery will work.

Yes, the _forum_ is about helping people and sharing information. That doesn't mean forum members are entitled to say everything they know or give information they suspect may not be used properly/responsibly. Free to help/share as much as they please. 

You see, some people can follow a written procedure to the "t" and it goes fine. Some people can follow a written procedure to the "t" and it goes wrong. Some people just can't follow any advice, so why give it? FWIW, that's just me sounding off in general. 

In any event, steel wool should be everywhere in the world. Find it, use it, make some money. Save every drop of solution until it's tested, then make sure it gets managed responsibly.


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## butcher (Jun 7, 2014)

I have to comment on how helpful Lou has been to this forum, sharing his hard earned knowledge, in many aspects of chemistry and science, and especially in the recovery and refining of the platinum group metals, we are very lucky to have had Lou, who has worked very hard to learn, and have him so generously share his valuable knowledge, with us, for that all most any of us can say is
Thank You Lou.


I have to agree with Lou as far as help goes on this forum, we are not here to help someone get hurt, or get into situations over their head.
And not everything will be shared, sometimes the explanation will be too complicated, dangerous, or sometimes it may be a mans bread and butter, which if given away may lower the bread on this mans table, but in general this forum has given us all a wealth of information, with that and with our own resources and study has been a very valuable gift to us all.

We have to consider also, much of what has been given by members of this forum has been held secret from the general public most of mans history, but with the forum has been shared freely, also giving us a resource for study, that for many of us, would not have had the opportunity to learn it otherwise, what is shared should be considered a very valuable gift, not all secrets will be shared, I guess that is just the nature of secrets.


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## justinhcase (Jun 8, 2014)

Just thought as no body has mentioned first aid I would point out.
Any one with cyanide on the premises on top of the having excess quantity's of alcali.
It would be good to have some ampules of Amyl Nitrite on the wall next to any station one might accidentally come into contact with said toxin.
Immediate inhalation of the stimulant is the only real antidote available as it is the only thing that act's quickly enough.
Then followed by an infusion of 300 mg or 10 mg/kg IV sodium nitrate,to be injected over 2-5 minutes, and a 12.5 g sodium thiosulfate IV to be administered over 10 minutes you may repeat both if necessary will give you the best chance of survival.
I know all the legal eagles will say first aid should not cover direct medication but I would much rather take my chance's with a little self medication than wait the half hour or longer that help would take.
This is one instance where seconds count.


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## goldsilverpro (Jun 8, 2014)

The amyl nitrite ampules are called "poppers" in the illegal drug trade.
https://en.wikipedia.org/wiki/Poppers
https://en.wikipedia.org/wiki/Amyl_nitrite

In most of the refineries I worked in, we kept a box of these handy, but I don't remember anyone ever having to use them. It takes a prescription to get them (at least, legally). They are not cheap. I think they are used in case of HCN gas inhalation, which is emitted when cyanide is mixed with any acid. I think the thiosulfate plus sodium nitrite is used for cyanide ingestion. It seems there are better antidotes available today but I think they require administration by IV.
https://www.google.com/search?q=cyanide+antidote&ie=utf-8&oe=utf-8

I remember reading that, when Paul Lynde died, a bottle of butyl nitrite, which produces the same effects as amyl nitrite, was found on his nightstand. This could have been the cause of his fatal heart attack.
https://en.wikipedia.org/wiki/Paul_Lynde

One on the most famous cyanide poisoning events was when a worker died in a Chicago company that was processing scrap x-ray film with cyanide/peroxide. There was even a 60 Minutes segment on it. Most everyone back then used cyanide for film but this changed abruptly after this death. Technically, cyanide is still about the best thing to use for film, since the silver is simply plated out and the solution reused. 
http://www.chicagoreader.com/chicago/murder-in-the-air/Content?oid=875834
https://www.google.com/search?q=%22film+recovery+systems%22+golab&ie=utf-8&oe=utf-8

I knew a guy in a film operation that fell into a vat of cyanide solution (as he told me, he was completely submerged) and somehow lived to talk about it. When I knew him, he was still working for the same company, which had long since converted to caustic soda.


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## kjavanb123 (Jun 8, 2014)

All,

I saw this in a shop, can this be a good substitute for steel wool? Plus it can spin inside the cyanide solution for agitation.




And



Best regards,
Kevin


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## butcher (Jun 8, 2014)

That tool has much better uses; I say no this tool would not work well for your purpose, too many other metals involved in the steel that this tool is made of.
Although steel contains iron, these are very different in many aspects.

Steel wool should be fairly easy to find, I do not know if you have hardware stores handy, if so check them, steel wool is often used as a pad for wood sanding or wood finishing.

Laminates from transformers or electric motors is a good source of fairly pure soft iron, these thin laminate iron plates, may work if you cannot find the steel wool, if you use these, after separating the laminates incinerate to burn off shellac and rinse of ash prior to trying them, (I would not burn of the shellac and rinse the iron until I was ready for use, to keep them from forming rust).


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## kjavanb123 (Jul 5, 2014)

All,

I had two plates of non-magnetite stainless steel cut to 6x6 inches submerged them partially into cyanide solution, connected them to positive and negative charges set the ampres to 4A, and voltage to 3V, but when I ran the rectifier ampreage was 0 or another word no current was going, could this be because of clips that connect the SS plates to rectifier were a little rusty? Or is cyanide solution non-conductive?
I can easily dissolve all gold plating items in a cyanide solution but when precipitate with zinc I get nothing.

Thanks
Kevin


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## Charles Connor (Jul 8, 2014)

Cyanide solution works as an electrolite by meanings of gold plating, which means it does works transfering electrons...
Double check your connections?...


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