The benzidine technique for histochemical detection of the SO4 ion.

The benzidine technique for histochemical detection of the SO4 ion was studied analytically on filter paper strips loaded with 0.02 ml of solutions of sulfate containing and sulfate free substances. The influence of the benzidin solution pH on the SO4 and PO4 ion precipitation was analysed and the experimental condition where the SO4 ion was specifically precipitated was established.