Question

Is thiocyanate ion a test for ferric ion?

Answer 1

Thiocyanate ion is a test for the ferric ion, `Fe^(3+)`.

Explanation:

Addition of sodium thiocyanate to ferric salts gives the blood-red complex, `[Fe(N=C=S)(OH_2)_5]^(2+)`. I think the ligand binds thru the nitrogen.

And `Co^(2+)` gives a blue complex. This was in fact used as a screening test for the presence of cocaine (i.e. it is used in the field, because it gives a visual determination). Only problem is that such a test for coke is completely unreliable, and a lot of people were wrongly arrested on the basis of this test.