Spectrophotometric and cytochemical studies on azures A, B and C

The cytochemical use of azures A, B and C, propared with either N HCL and potassium metabisulphite or with sodium hydrosulphite in tissue sections were investigated. Both in situ absorption curves of nuclei stained with each of these dye-SO2 reagents as well as in vitro absorption data of acqueous solutions of the dyes are also presented. It has been pointed out that the mechanism of staining with azure A-SO2 and azure C Eosinate-SO2 is the same as that of the conventional Feulgen reaction with Schiff reagent but that of staining with azure B-SO2 is by the modified Feulgen reaction because this dye does not contain any primary amino group.