P 2188 (OTTO) Potassium chromate ACS reagent, ≥99% Cas 7789-00-6 - used for laboratory work in situations where an anhydrous salt is required. It is as an oxidizing agent in organic synthesis. P 2187 (OTTO) Potassium chromate, GR 99%+ Cas 7789-00-6 - used as in qualitative inorganic analysis, e.g. as a colorimetric test for silver ion.