Friday, September 24, 2010

A Substitute for Aqua Regia

While not of any immediate use to us polymer people, I have some colleagues that use immense quantities of aqua regia and they found this interesting. Aqua regia as you may recall is a 1:3 mix of nitric acid and hydrochloric acid able to dissolve both gold and platinum. But now there's a (semi-) organic option:
[They]serendipitously discovered that gold dissolves when it is left in a mixture of thionyl chloride (SOCl2) and the organic solvent pyridine. Further experiments on the system revealed that other organic solvents and reagents - such as N,N-dimethylformamide (DMF), imidazole, and pyrazine - could achieve similar effects when mixed with thionyl chloride, with the gold recoverable by subsequent calcination.
Thionyl chloride is not exactly the finest chemical to work with, but it is very common in organic labs (I've used it myself to prepare acyl acids needed for to make custom polyamides). And pyridine with its pile of dead fish smell is no great shakes either, but again, commonplace for organikers.

But further, they also found that by adjusting the ratios of the solvents, they could selectively dissolve gold or platinum, a trick not possible with the acids.

1 comment:

Anonymous said...

hi, new to the site, thanks.