Alternate poor man AR (battery acid + chlorox)

[Stowmaster]

I want to test alternative aqua regia by the scheme:
4H2SO4 (+excess) + 4NaOCl = 4NaHSO4 + 2Cl2 + 2H2O + O2
I plans to dissolve the gold dust and husks, obtained after dissolving in nitric acid IT pins.
Advantages: no nitrates.
Disadvantages: It is unknown, will there be sulfur dioxide, and its possible effect on gold.
Before the test, I want to get the advice of experienced professionals.

 

[bswartzwelder]

I AM NO CHEMIST! Having said that, AR (called Aqua Regia) or Royal Water has been around for centuries. It got its name for the fact it would dissolve gold. The ancients knew it would work and that's what they used. That's what is still used with great success even today.

I doubt your experiment will meet with great success. Sulfuric acid IS USED WITH GREAT SUCCESS to remove tin and lead from gold on circuit boards. While we want to get rid of base metals like tin and lead, using a solution which will dissolve them is counter productive if you dissolve your gold with them. The gold will have to be precipitated and the tin and lead left behind. Or, you might be able to drop the tin and lead first leaving your gold behind. As has been said on the forum from its inception, "Don't try to reinvent the wheel.". Your experiment won't yield any results that have'nt already been studied. Sulfuric is more dangerous and more expensive than Hydrochloric. I would recommend sticking to what is known to work. By the way, READ HOKE. All your results will most likely be there.

 

[Stowmaster]

I do not see any problems in the impurities of Sn and Pb. But I think, that no lead or tin anymore. Insoluble sulfates, even if they will fall out and the sediment will be easily separated.
The big fear at me is a possible admixture of iron, FeSO4, and its consequences.

 

[solar_plasma]

Most likely you will form some hypochloric acids, which will gas off. I do not believe it will work for your purposes. Battery lead normally contains cadmium so it's better to cast. Correction welcome.

 

[Traveller11]

Most likely you will form some hypochloric acids, which will gas off. I do not believe it will work for your purposes. Battery lead normally contains cadmium so it's better to cast. Correction welcome.

What is hypochloric acid?

 

[solar_plasma]

sorry, Hypochlorous acid

 

[solar_plasma]

But you can use sulfuric and chlorides to make HCl. Just search for the description.

 

[Platdigger]

About a hundred years ago they used bleach and sulfuric acid to release the chlorine to leach gold from ores.

Read the first chapter of Ammens "second edition".
nothing new

 

[Traveller11]

About a hundred years ago they used bleach and sulfuric acid to release the chlorine to leach gold from ores.

Read the first chapter of Ammens "second edition".
nothing new

Yes, they placed calcium hypochlorite powder and sulphuric acid into a mix of water and ground ore, releasing chlorine gas, as you said. However, that is only part of the formula. The cylinder they used for leaching was also airtight, and filled to the point, with ore and water, that, as chlorine gas was released, it immediately began building pressure inside the cylinder. This served two purposes: 1) chlorine gas dissolved in the water, making hypochlorous acid and 2) the resulting elevated pressure prevented the hypochlorous acid (HOCl) from decomposing by losing its oxygen atom to the atmosphere. If HOCl was allowed to decompose, it became HCl and lowered the overall pH of the leaching solution. It was critical to avoid this, as the ores contained many iron oxides that would break apart in acidic conditions, releasing iron, and causing the leach to dissolve iron instead of gold.

 

[Platdigger]

Yes, that is right. I should have mentioned the barrel was sealed.

 

[Traveller11]

Yes, that is right. I should have mentioned the barrel was sealed.

I've just completed a tabletop model of this unit and I will try to post some photos of it later tonight (first I have to figure out this new digital camera and how to connect it to my computer). It is constructed mainly from 3" ABS pipe and fittings and an electric reduction motor that turns about 39 rpm.

As the chlorine solution the oldtimers were making seems to be, from all the research I've done, a solution of sodium hypochlorite/ hypochlorous acid at a pH of between 6 and 8, the method I have chosen to make this solution is adding acid (either hydrochloric or acetic) in small amounts to regular Clorox bleach, testing the pH of the solution between additions of acid, and slowly bringing the pH of the bleach to 7-7.5. This will convert roughly half of the sodium hypochlorite to the more active hypochlorous acid. Before adding this solution to a mixture of gold bearing black sand/clay and water I will, following the advice of several patents, add sodium or calcium chloride to the mixture.

In the leaching chamber I designed, it is possible to add chlorine solution in such a fashion as to exclude all air from the chamber and seal the chamber. I believe this allows the hypochlorous acid to go to work on dissolving gold instead of decomposing and turning to hydrochloric acid as, under pressure, it cannot lose its oxygen atom to the atmosphere. I have proven this several times in the small water system I operate here. We add chlorine as a disinfectant to drinking water in the form of sodium hypochlorite. As the pH of our water is typically 7.5, the free chlorine in this water exists as a 50/50 mixture of sodium hypochlorite/hypochlorous acid. In our pipelines, at 90 psi, it takes about two weeks for this free chlorine to drop below levels that can be measured. However, the same water, poured from the tap into an open container, will lose all of its free chlorine within an hour. I believe this fact is what allowed the oldtimers to be successful leaching gold from their ores.

 

[FrugalRefiner]

A lot of this is discussed in T. K. Rose's The Metallurgy of Gold. I've just been reading it for the first time myself, but there are several chapters devoted to preparing ores (crushing, roasting (which is much more complicated than just heating it up), etc.), chlorination in both vat and barrel processes, precipitating, etc. It's an old book from 1894, so it's freely available on Google books. I'm considering it for a future printer friendly version project some time in the future. It's a very informative book.

Dave