Silver Dichromate, Ag₂Cr₂O₇

Silver Dichromate, Ag₂Cr₂O₇, is prepared by the addition of silver nitrate to a hot solution of potassium dichromate containing a large excess of nitric acid, and cooling till crystallisation occurs. The salt may readily be recrystallised from nitric acid, traces of which are, however, retained. It crystallises as red-black plates in the triclinic system, and has a density of 4.770. It cannot be dried without decomposition, for it is readily decomposed by water with formation of the neutral chromate and chromic acid.

No trichrornate of silver is known, but a chromoiodate, AgCrO₃.IO₃, a chromicyanide, Ag₃Cr(CN)₆ and a chromithiocyanate, Ag₃Cr(CNS)₆, have been described.