Removing gold for high school experiment?

[marianne.lavidis1]

Dear All,
I am a high school teacher from Australia and have access to a fume hood, good chemicals etc. I was wondering if I dissolve a few samples of gold plated e-waste in concentrated HCl just to get gold flakes what dangerous fumes would result? Do I need to use peroxide to activate, or would the students get a visible result.
Also, are there any dangers in the TnCl2 test I am seeing for the filtrate? I think there is some great chemical experiments here but don't want to do anything dangerous, just fun. I would not like to expose them to mercury for instance, we don't even use mercury thermometers!
Thanks for your help!
Marianne

 

[kernels]

35% Nitric Acid will relatively quickly dissolve the copper under some gold plated fingers from RAM modules, this will leave you with some nice gold 'foils'

You can then wash these gold foils and dissolve them in Aqua-Regia, cover them with HCl, heat to 70 degrees Celcius and add small increments of Nitric Acid until the foils are dissolved and the solution is a nice golden yellow.

You can then do the experiment with Stannous Chloride to turn a small amount of the solution deep purple.

You can also put a piece of copper into the solution to show a single-displacement reaction where copper goes into solution and the gold cements out as a brown powder.

 

[nickvc]

To add to kernels post, when you dissolve metals in nitric you get noxx fumes, if you then dissolve the resultant foils in aqua Regina more dangerous fumes are released, this should be safe under a decent fume hood with good extraction, also bear in mind nitric and aqua Regina are very strong reactants which can do great harm to human tissue but used carefully in a controlled manner it should be safe but wear gloves and eye protection.

 

[g_axelsson]

That would be "nox" or "NO_x" and "aqua regia".

As Harold doesn't post any longer I feel it is my obligation to be the spelling police. :wink:

Göran