Pitch black solution - need help

[butcher]

Wingedcloud,
Keep it up your learning, and sharing what you are learning, that is what we do here.

 

[Topher_osAUrus]

I was thinking about this earlier while i was working on my car, and remembered i had recently participated in another thread dealing with tin in AR.

Here is a quote from it

From what I understand... haven't done the test myself, so I'm speaking theoretically.

The use of excess nitric acid will oxidize any stannous tin into stannic tin, keeping it from creating a colloid. Some stannous tin will reduce gold chlorides into metallic gold and in so transform into stannic form. Any colloidal gold will be redissolved as long as there is any free nitric left.

So in the end, the only time you risk creating a colloid is when you haven't oxidized all tin to 4+ state and is out of nitric acid (or nitrate salts together with hydrochloric acid).

What I have tested is creating a colloid in aqua regia by dropping tin chloride into it. It created a beautiful red reaction that disappeared within seconds when the colloidal gold was redissolved.

One problem with metastannic acid is that the liquid locked up in the tin mud will contain dissolved gold. It can be extracted by filtering but the tin will clog the filter badly, slowing it down to a crawl. Or extracted by repeated decanting and dilution.

For example if you have 100 g of dissolved gold and can extract 90 percent of the liquid by decanting you still have 10g of gold mechanically locked in the remainder mud. Fill it up to the same volume, stir well and let it settle. This time you recover 90prcnt of what's left and only 1g is still locked in the tin mud. Repeat as many times you need to recover additional gold until the value left is too little to worry about.

I might be wrong in this and missing some way that the metastannic acid would lock up the gold and I hope someone will point it out then.

Göran

But, it appears you have already solved this particular dilemma.

Looks like gold to me! And, any gold...is good gold!

 

[Wingedcloud]

Wingedcloud,
Keep it up your learning, and sharing what you are learning, that is what we do here.

Will do, sir !