Unknown Chemical

Chromate: The chromate ion is yellow, the dichromate ion is orange. Both can be confirmed by the addition of sodium hydrosulfite. If a yellow or orange solution is strongly acidic, adjust the pH to slightly acidic before you add the hydrosulfite. The yellow Cr+6 ion will be reduced to the green Cr+3 ion. (Chromic acid that has been used for cleaning may have already turned green.) Chromate can also be detected by adding a few drops of lead nitrate to the unknown; a precipitate of yellow lead chromate confirms.