Difficulties in ferrous iron mordant hematoxylin staining and some hematoxylin substitutes.

A gradual deterioration of intensity of sequence ferrous sulfate hematoxylin staining was traced, after elimination of hematoxylin quality as a cause, to a deterioration of the metal salt, associated with caking of the crystals. Fresh samples were also partly caked and ineffective. Ferrous ammonium sulfate was found also subject to the same deterioration. Ferrous chloride freshly prepared as a 1 M solution from iron wire under anaerobic conditions at biweekly intervals proved to be satisfactory as a mordant source. Of several other mordant dyes tested: gallein, brazilin and chromoxane pure blue B were the best, but none was equal to good hematoxylin.