Making Genuine Gold Powder from Precipitated Gold?

Thanks for this great help.

Hi, Ghulam. This site has more than 50,000 threads and most have good responses. In this case, perhaps no reader has ever heard of a procedure to make a proper yellow and lustrous gold powder by electroplating, and there may be none :-(

Like me, the readers may doubt that such a procedure exists, but they may not have the universal experience and the hubris to feel qualified to post here that "No, no such procedure exists!"   :-)

Regards,

A. Gold particles that precipitate with SMS are normally very small in size -- with dilute solutions the particles will be even smaller. Concentrated solutions reduced with sulfur dioxide gas will give a larger particle size, like fine sand. Heating the solution might help increase the particle size slightly as it may cause the particles to stick together. Sulfur dioxide gas works the best of all the reducing agents in providing the largest particle size gold precipitates making them easy to wash and will yield the highest purity. As I recall from previous trips to India, sulfur dioxide gas was difficult to obtain there.

A. Helga,

There are other precipitants that may work better. I believe that hydroquinone or oxalic acid ⇦this on eBay or Amazon [affil links] will produce a lighter color powder. They would still not produce bright shiny gold, however.

If the brown gold powder you produced from ferrous sulfate ⇦this on eBay or Amazon [affil links] is pure, it should burnish to a rich gold color. To test this, put a small piece of the dry powder on your fingertip and rub it hard on glass. I don't know how burnishing would work if the powder were in a dried paint matrix. Might work well.

If there are any references to making real gold paint, I would imagine it would be made from crumbled gold leaf.

There are also real gold products like Hanovia Liquid Gold (made by Engelhard) , that can be painted on and then fired. These are commonly used to decorate glassware and ceramic objects.

A. The question is quite old, so the original questioner has probably long ago found an answer-or more probably, bought the commercial product suggested. I found the quest/ans when looking for the ionic solution to precipitate the highest concentration of gold dissolved from junk jewelry. (Additionally: since the chemical reaction is an equilibrium reaction, the gold will always contain a very small amount of the alloying metals, usually copper, tin, and others, even after chemical purification.)

However, since someone else is likely to have the same question, I will post this.

Gold paint is most probably composed of tiny flakes of gold leaf-flat, very thin plates that remain 'float' in suspension but are large enough to reflect true gold color. A gold precipitate, depending on the size of the gold particles, can, and usually does not appear golden. Just like when polishing, say sterling silver, with a cloth, the cloth turns black. This is because of the visible light reflecting from the very fine particles is trapped within the slurry; and essentially no light IS reflected-the visible wavelengths are 'caught' by the mixture of very small silver particles, silver tarnish, and granules of the polishing compound. (Polishing perfectly clean silver results in black as well, as does polishing brass, steel, etc.)

So, to make gold paint powder the gold needs to be precipitated-or joined into larger masses-perhaps not easily possible-or formed somehow into larger (still micro-scale) masses, and then flattened for best effect and gold reflection, perhaps by flattening between two highly polished very hard substances; two diamond surfaces come to mind, or a hard ceramic--or, maybe even Corelle Ware if its surfaces are flat enough. Again, the extremely small precipitant particles will reflect light among themselves trapping most or all of the visible light and therefore not appear gold, but any color (brown in your case) to the no color, black.

[An easier method for making small gold flakes just occurred to me which is much easier than 'squashing' gold:

Paint the pure fine mixture of gold precipitate on a high gloss, or gold-rejecting very heat resistant substance, say a ceramic tile, then heat the tile with MAPP gas or oxyacetylene, electric, whatever, above the melting point. A solution-actually just a suspended mixture of washed gold precipitate-in an acceptable layer thickness when dried will agglutinate, the micro particles will unite and form flakes. However, with many ceramics the gold will stick-fuse to the surface and one will end up with a beautifully gold-flaked tile. But, some substances do not 'like' gold, and the gold can be brushed or scraped off. Finding these refractory materials should not be hard; I would start with the high temperature silicones (not silicon or silicate). At the worst you can have a 24 carat tile, which you may want to dissolve the gold from and began again. Please wear face protection and, Good luck!]

Interestingly, fine gold particles suspended in glass, a supercooled liquid, not a solid, appears a rich, beautiful red that was (is?) used to color the glass used in stained glass in churches, etc.

If I find a method for producing larger gold flakes during my chemical cation (+ ion), or complex ionic compound search to purify gold in one or two steps, I will pass it on.

Harvey
(OldAlaska)

A. Hi Thomas. Gold will not dissolve in hydrochloric acid; you need aqua regia or an imitation aqua regia made by adding sodium nitrate ⇦this on Amazon [affil link] to the HCl. There are at least three well known books on gold recovery (Ammen, Gee, Hoke) -- the shortest of which is 400 pages, so there's an awful lot to the topic. Dissolving metals, especially those as noble as gold, obviously involves very powerful chemistry not household ingredients ... so it includes environmental problems, and serious safety issues that unfortunately you can't learn from a paragraph or two in a public forum.

If you have gold fever and cannot be dissuaded, but aren't willing to read a book either, then purchase a system which comes with instructions and supplies as it can partially mitigate the dangers. Good luck.

Regards,