Gold Tin compound

[qst42know]

Just to satisfy my own curiosity can one of the more chemistry oriented members tell me if this chemical structure is responsible for very fine gold precipitate in the presence of tin. I know precious little of chemistry but this structure looks, well for lack of a better term (closed).

http://www.rsc.org/publishing/journals/CC/article.asp?doi=b416472e[/b]

 

[Lou]

Basically you ask about the Purple of Cassius test, a test that gives about 9-12 ppb in precision (and +/- a few ppb if done colorometrically with a really great absorption curve)

Tin chloride is kept in acidic conditions because it hydrolyzes to its basic chloride. Tin (II) would really like to go to tin (IV) species, this means it is a good reducing agent, as it becomes oxidized. This is why you should keep a bit of pet ether or xylene on top of your stannous solution if you plan to keep it--also, leave some tin in the bottom, it will further prevent oxidation.


What happens is a redox between solvated, complexed Au (III) and acidic Sn (II). The gold is reduced to its ground state, while tin moves up in oxidation. The gold is in a very, very fine form, below a micron in size if I recall. This sticks to the surface of the formed suspension (technically a colloid) of basic stannic hydroxide which exists with SnCl4 that couples with it a la charge interaction. That nano fine gold on the surface is what makes it the purple color.

There is no real ''official'' complex with it like there is for Pt and the PGMs but that may be argued.

 

[JustinNH]

awesome post 8)

Thanks Lou

I was wondering about this topic and figured id give the search button a try before i duplicated a post.

See folks, the search button saves people's time