Abstract
The alum is one of double salts of sulfate and its aqueous solution is highly acid. Lithium alum and cobalt alum are useful in staining the peroxidase positive granules of leucocyte blue or bluish violet, while the other nine alums are unsuitable as far as the fixation and peroxidase staining of blood cells are concerned. Most of alums except cerium alum belong to the Salt I after Mitsui and Ikeda, in other words, their saturated aqueous solutions become inhibitor of this histochemical peroxidase reaction. Furthermore all of them lose their potency within a day when mixed with the benzidine-hydrogen-peroxide solution in a test-tube before the staining.
