The Perfect Gold Refine from karat jewelry.

[LittleJohnnyH2SO4]

How about using isopropyl nitrite as a means of purification? That is, mix the crude nitrite with a slightly less-than-stoichiometric amount of sulfuric acid and a slight excess of isopropanol in an ice bath. Remove the oily layer of isopropyl nitrite that forms (nitrate does not react), and react with a solution of a slightly less than stoichiometric amount of sodium hydroxide. This leaves a solution of pure sodium nitrite in water and isopropanol, which can be removed by heat of left to evaporate.

Distillation would yield a slightly more pure product, I suppose, but is probably unnecessary for most uses. Isopropyl nitrate is a vasodialator. It can be used as part of an antidote kit to treat cyanide poisoning, but is probably better known as a close relative of "poppers." With this in mind, you should avoid breathing fumes, but since you're all used to working with concentrated hot acids and NOx, this should be easy. It also avoids the need for silver (and making silver nitrate at the cost of your nitric acid), exchanging it for cheap-as-dirt isopropyl rubbing alcohol.

 

[butcher]

johnny what are the dangers if any of expolsives? proportions? sounds dangerous is it? any chances of making R-NO2?
this sounds like organic chemistry?

 

[Lou]

This was a good suggestion.

Only issues are the volatility and flammability, but using an ice bath should minimize this.

I suggested silver mainly because silver is commonplace to most of us here (it's used in inquarts) and it's fully recyclable.

 

[LittleJohnnyH2SO4]

johnny what are the dangers if any of expolsives? proportions? sounds dangerous is it? any chances of making R-NO2?
this sounds like organic chemistry?

The produced substance is a nitrite ester of an alcohol. This is flammable, more so than the starting alcohol, but it isn't explosive. Also, if you intend to destroy it immediately, it shouldn't be around for more than say 20min. I don't think there is any chance of making R-NO2 in these reaction conditions. That would form in probably a low yield if you were to mix isopropyl chloride, bromide, or iodide with NaNO2 in a strongly basic solution. This uses the alcohol in an acidic solution. We are producing R-ONO. Subtle structural differences make a lot of difference.

This is basically what you'd be doing with a hydrolysis step added. A pipette or dropper can replace the needle. I'm not sure how necessary the stirrer is. I suspect that it is not essential except to aid keeping the reaction cool, which manual stirring can probably achieve: http://www.youtube.com/watch?v=ygAxh81WaWg

Ill do some tests and report proportions. I can give you theoretical, but functional procedure is another thing.

I have pounds upon pounds of nitrate, but no nitrite, so I'll be making my own. There is a 5 page discussion on nitrite synthesis on sciencemadness.org, which makes reaction of nitrate with molten lead seem to be the best option. However, I don't think anyone quite did Lou's method as stated here, so I'll give that a shot first. It sounds good, except I question the red heat part. Nitrite decomposes further at fairly low temperatures. Were you able to verify nitrite formation Lou?

 

[butcher]

Thanks, two chemist on the forum make my head spin, more knowledge than my lil brain may be able absorb.

 

[SilverNitrate]

On page 124 in Ammen's first edition, he gives a procedure for precipitating gold with sodium nitrite, although he doesn't say how much to use. He evaporates to eliminate the nitric, dilutes to 5% acid or less, and then adds the sodium nitrite, either dissolved or in solid form. If the gold doesn't drop, he dilutes further or adds a pinch of baking soda to reduce the acidity. If all is right, the gold should drop immediately. The amount of acid is critical. I see traces of all this in your procedure, although you've seemed to complicate things enormously.

What is your purpose of also adding oxalic acid?

A long time ago, I read that the addition of ethyl alcohol could be added to AR to eliminate the nitric. I tried it once and didn't like it, especially the horrible smell. I seem to remember that Lou mentioned some potential dangers (explosive?) in using the alcohol.

If you only use exactly enough nitric to dissolve the gold, and no more, evaporation or urea or alcohol are not needed. You just dissolve, dilute, settle, filter, and drop the gold with a sulfite. If a second AR is needed, it can be done very quickly. I have detailed how to do this many times on this forum.

I have read many times on the internet that sodium nitrite can be easily made by heating sodium nitrate, although no one gives an exact procedure.

First, i'm not suggesting a way to make sodium nitrite. And since sodium nitrite and SMB are considered food additives, they are generally available. True SMB drops more gold per amount than sodium nitrite, but I find the SO2 fumes harder to handle than the NOx fumes.
The use of oxalic acid is to form a precip of copper oxalic- in solution as the gold drops the particles have something to cling to, and tend to drop faster. The use of ethyl alcohol is simply to act as a de-frother as this reaction will form lots of sudsy bubbles. The addition of alcohol is after the AR has been diluted of its strong acids with NaOH. And since the gold drop occur with solution of room temperature, there is no risk of forming explosive. The aount of alcohol is equal to only 2 or 3 spoonfulls for a 1000+ml amount of AR yielding 5+ ounces pure gold.

 

[goldsilverpro]

Doesn't anyone on this forum understand that, when dissolving gold, if you don't add any extra nitric, you will never have to eliminate the nitric. It's so simple. The chemistry of refining gold is so simple. Why make it so complex?

 

[lazersteve]

GSP,

I hear you loud and clear. I've been using your 'controlled nitric' additions since you posted it last year.

Thanks for the tip, it really works nicely and is very conservative on the nitric acid.

I've been in the habit for some time now of adding my nitric out of a dropper bottle in small increments. It's the only way to fly with AR. The same principle applies to poor man's AR when using sodium nitrate and HCl.

Steve

 

[Noxx]

Same for me, but I've been using a pipette...

 

[Platdigger]

Butcher said...
"Thanks, two chemist on the forum make my head spin, more knowledge than my lil brain may be able absorb."

I see your point Butcher....wow

but hey......I like it.......I think it is great!

lernins good right?....


Randy

 

[Lou]

Johnny's absolutely right! I was thinking of another reaction that requires heating something to a dull red heat (470C) with charcoal. Any nitrite or nitrate would be made into NO2 at those temperatures.

For reference:
Sodium nitrite melts at 271 and decomposes at 320.
Sodium nitrate melts at 307.
Potassium nitrite melts at 441 and decomposes violently at 538.
Potassium nitrate melts at 337 C and decomposes at 400.

I know it can be made by melting with lead, which melts at 328 C--sodium nitrite will be decomposing at the temperature at which lead melts. So that method is obviously suitable for KNO2 only.

Before you try this, let me try it once more to check my memory. Thinking on this again, it might not be a good idea to heat a reducing agent with a strong oxidizer. So please hold up for now.

Edit: I checked around on the method and I was close to right. There is a huge difference between being close to right and absolutely right, especially in chemistry.

The method does work, but it should be conducted at a lower temperature.

We'll talk about this more after I try it again and make some better notes on it.