HISTOCHEMICAL RECOGNITION OF CALCIUM OXALATE

Abstract

Of the workers applying the von Kóssa test to calcium oxalate crystals in animal tissue, about half reported blackening in silver nitrate on exposure to light. We found that "pure" calcium oxalate crystals, produced in rats by the administration of ammonium oxalate or ethylene glycol, gave a negative von Kóssa reaction. These crystals, however, were blackened when treated with a solution of silver nitrate in concentrated hydrogen peroxide. Other von Kóssa negative salts, such as CaF₂ or CaSO₄·2H₂O, do not respond to the H₂O₂ and AgNO₃ test.