Although the Von Kossa technique is used to demonstrate calcium, it actually demonstrated the anion rather than calcium itself. This is usually carbonate or phosphate. Usually the cation is calcium, so the method is commonly considered to demonstrate that material. However, urates are also blackened, and it should always be born in mind that some other anion could be being demonstrated.
5µ paraffin sections of neutral buffered formalin fixed tissue are suitable. Other fixatives are likely to be satisfactory, although those containing strong acids may remove some calcium deposits..
Culling C.F.A., (1974)
Handbook of histopathological and histochemical techniques Ed. 3
Butterworth, London, UK.
Last updated Aug 2005.