Can't find nitric acid for refining electronic scrap anymore

A. Franklin

If you do not require large volumes, you might try Rocky Mountain Reagents in Denver. Otherwise, there is Interstate Chemicals in Pueblo.

A. Hi Franklin,
Unfortunately I don't know a way of dissolving the base metals without the use of nitric acid. Have you considered using a non-cyanide gold strip (normally sold in powder form), then dropping the gold out of solution? You will need a few tanks, heater, mixer, but in the long run it may be cheaper for you. I'm not supposed to mention suppliers on this website, but there are a few good companies headquartered in Rhode Island which have much lower cost minimums, and the ability to help with any questions you may have regarding product. You could use Thomasregister.net under precious metals for electroplating or plating chemicals. If you don't want to go that route have you tried local laboratory supply houses to buy in smaller amounts? Just some thoughts ... Good Luck!

A. They pulled ammonium nitrate off the shelves because of its key roll in meth amphetamine production, but sodium nitrate ⇦this on Amazon [affil link] or nitrate of soda found at most garden suppliers works just as well. I dissolve it in cold water until no more dissolves then add Liquid Fire or Roto acid drain cleaner ⇦this on eBay or Amazon [affil links] 98% sulfuric until it turns orange and fumes red this generates a lot of heat and boils; use it right away. Much more effective than battery acid and ammonium nitrate due to the heat generated.

A. These procedures sound so dangerous that they should be labeled "Professional driver. Closed course. Do not attempt". The internet is a giant one-room schoolhouse, folks, and not every lesson you overhear may be appropriate for your experience and training level :-)

A. Franklin you can get ammonium nitrate in instant ice packs, the kind that comes in first aid kits and medical suppliers.

A. Grainger.com sells nitric in small quantities.

A. I found Nitric acid 67% at www.xelexo.net

Hi,
They banned H2SO4 too.
No longer possible to buy it; even battery acid and drain openers are banned and taken out from whole markets.
All brands are replaced with some useless rubbish gel instead of acid.

If it's still available in your location then hurry to buy it for your future usage because soon it will be forbidden everywhere.

Good luck,
Tom

A. I cut up clean gold plated scrap, put 1 lb potassium nitrate stump remover (or other nitrate fertilizers) in gallon pickle jar, this is in pot of sand on a hot plate outside, made a Teflon lid with hole in it which poly hose runs to another bottle small-neck with little water in bottom of it, boil new battery acid to concentrate, cool as not to shock thermally glass, pour into gallon jar of scrap and KNO3 put lid on, tape Teflon then electrical then cloth.

Also tape other jar with hose into bottom so NO2 gas will bubble through H2O,
KNO3+H2SO4+Au+Cu = HCuSO4+Au+NO2+H2O
This dissolves base metals except gold, platinum, etc. The NO2 bubbled through H2O gives NO2+H2O = HNO3 68%. I save this for cleanup testing. etc., boiled until no more NO2 gas seen in jar and solution color changes green to blue, and gold flakes float easy. Cool, pour solution off gold flakes to another jar; add water to prevent copper sulphate ⇦this on eBay or Amazon [affil links] salts crystallizing, let settle to recover a little Au that settles. I save this blue copper sulphate for electroplating, etching copper, electrowinning, root removal in sewer lines, fungicide, soil amendment, algaecide for ponds, or to make other copper salts, etc. Or add aluminum and baking soda [in bulk on eBay or Amazon [affil links] to make safe for disposal. Done properly this is safe and environmentally and economically acceptable. We capture the gases that normally go into atmosphere or lungs and reuse them safely.

A. Acid peroxide (HCl + H2O2) will dissolve base metals. It's not as nasty as nitric and it's readily available. I use it to strip gold from cutoff fingers and CPUs.

A. Hi Brett. Yes, nitric acid will dissolve most metals you encounter, like copper (probably not aluminum and some other metals).

But "safely" for people who don't need no stinkin' badges from having taken chemistry, and who know they should leave it to the pros, but are instead driven by gold fever? Are you kidding?  :-)

Luck & Regards,

A. Nitric acid will dissolve most base metals if the gold content is about 25% or less. If higher, the undissolved gold will coat the bar and block penetration of the acid. Hot dilute nitric (cut at least 50% with water, by volume) will work better than concentrated nitric. It takes about 1/2 gallon of concentrated 70% nitric diluted to one gallon with water to dissolve a pound of base metals.

There is likely some tin, from solder, in the bar. If so, the nitric will form metastannic acid ⇦this on eBay or Amazon [affil links] with the tin. This is a slimy gunky material that will make filtering quite difficult.

All in all, this is probably a very non-profitable way to get the gold. It shouldn't have been melted all together in the first place. If you're lucky, you might get about $20 worth of gold from a one pound bar.

If you do this, be safe. The fumes are quite toxic and must be exhausted. Use a good fume hood.

A. I guess I should have first asked you what type of parts were melted. If they were small to medium sized connector pins that were completely gold plated, they might run as high as $80/pound. If the pins were only partially plated (common) or, if the pins were of a large diameter and were comparatively heavy in weight per pin, they could run much less per pound.

I may be wrong, but this sounds like the bars made from melted pins that are now being widely offered on online auctions. In most cases that I have seen, these are made from lo-grade pins. If the seller were to list these pins as is, unmelted, the photos would show them to be lo-grade. By melting them, their visual identity is erased. Buying these is always a pig-in-a-poke, no matter what the seller claims.

Connector pins and circuit board fingers are plated, on average, with about 30 microinches (.000030") of gold. They might be plugged and unplugged into female connectors many times during their life-span and, therefore, the gold must be thick enough to exhibit good wear characteristics. About 30 microinches of hard gold plating has long been the average standard for this. Except for some CPU's and some military components, this is about the thickest gold plating you'll find on a modern electronic part. On other types of gold plated components that are not plugged into connectors, the gold can be as thin as 5 microinches. One square inch of 30 microinch gold plating has a value of about 36 cents, at the present gold spot of $1172/tr.oz. If thicker or thinner, the value is proportional to this.

Well you were right, Chris, about the amount of gold. So I used nitric and it pretty much ate up everything. From what I hear the bars like I got are 97% brass with about 3% gold. So I've moved on to different things. I have some military grade stuff that I was gonna try next but not without some gold stripper. I may just use the ole muriatic acid and hydrogen peroxide as it seems to work pretty good. I also have nitric for after to clean the gold once the other acid has done what it can. Seems to be working.

Oh ya for those who just want to make a hobby out of it ... DON'T. It's far more expensive than you think and you just have a bunch of acids that you have to discard. It's really not worth it. Sell what you have on an auction site or something. You'll make money instead of lose it. And it's safer :)

A. 3% gold would be over $500 per pound. It's more like 0.05%-0.40% for gold plated pins.

! I hope anyone using hydrazine knows that it is a carcinogen.

A. 2 parts muriatic acid, 1 part hydrogen peroxide. Cut gold fingers off computer boards, use tempered glass container or plastic. Put gold parts in container, cover with acid & peroxide. Do this outdoors. All safety gear. Chemicals will release the gold. Might take 3 days. Make sure there is no solder on the parts. Remove boards, filter liquid through coffee filter. You can do this twice. Liquid will turn green. look up scrapping on YouTube.