Simple test for KBr?

[G Benaim]

I have a dry powder unlabelled, which I'm pretty sure is potassium bromide. Is there a simple test to determine whether it is or not?

Thanks.

[Maris Rusis]

Until you know what it is be very very careful. Think of it as possibly potassium cyanide. If you get KCN powder on your hands nothing will save you. Death is certain.

With that caution in place the easiest test for a bromide is to make an aqueous solution of a sample of the powder. Then add drop-wise some sodium hypochlorite solution (laundry bleach) that has been acidified with a little hydrochloric acid. Don't add too much or the test fails. The reagent liberates free bromine which colours the solution orange-red.

To be really sure shake the orange-red solution with a little carbon tetrachloride or chloroform (say 2ml) and the bromine will dissolve in the organic solvent and form a coloured layer under the aqueous solution.

All this is easy in the usual inorganic chemistry lab but at home all I can say is be careful.

[John Bowen]

A pound of KBr costs all of $11.25 from the formulary. Why take the chance with an unlabled product? Toss the stuff and order some fresh chemicals. A pound will likely last you 10 lifetimes. I presume Maris has a valid test, but if you place any value at all on your time, you'll just order some from your favorite chemical supplier.