Author: Nat Pernick, M.D. (see Authors page)

Revised: 30 October 2015, last major update October 2013

Copyright: (c) 2003-2015,, Inc.

PubMed Search: von Kossa methodAlizarin red SAzan stain
Cite this page: Calcium. website. Accessed November 12th, 2018.
Definition / general
  • With routine staining, calcium forms a blue-black lake with hematoxylin, usually with sharp edges
  • von Kossa method: silver is substituted for calcium in calcium salts; light or a photographic developer turns the silver black; only stains calcium bound to an anion such as phosphate or carbonate; most useful when large amounts of phosphates and carbonates are present, as with bone
  • Alizarin red S forms an orange-red lake with calcium at a pH of 4.2; works best with small amounts of calcium such as in Michaelis-Gutman bodies; this method is used on Dupont ACA analyzer to measure serum calcium photometrically
  • Azan stain used to distinguish osteoid from mineralized bone.
Microscopic (histologic) images

Malakoplakia of bladder
(von Kossa calcium stain)