Non-Chemical getting rid of unused nitric acid

[goldnugget77]

Since I am unable to carry out these exercise live.
I am imagining how it might be to do the actually sampling.

I am at page 44 in the Hoke book
I am at where she says
(5) REMOVING EXCESS NITRIC ACID

Just before she said dissolve gold in Aqua regia
Just enough Aqua not more

Question 1 : Shouldn't I now be left with with AuCL3 (auric chloride)
I should be able to precipitate now with copperas or with SMB
whats this paragraph about getting rid of unused nitric acid

 

[Harold_V]

It is common for those without experience to use too much acid, so there is generally an excess of nitric present. While gold will precipitate from a solution that has traces of unused nitric within, too much prevents precipitation, so evaporation is suggested to expel all of it.

I highly recommend evaporation instead of using urea---although many use it and are comfortable with the results.

If gold is precipitated from solutions that bear traces of nitric, when the recovered gold is washed with HCl, you can expect a small percentage to be re-dissolved, until the residual nitric has been consumed. In spite of careful and multiple rinses, it is difficult to eliminate entirely.

Harold

 

[goldnugget77]

Hi Harold
Thanks for your help