Biocare’s CAT Hematoxylin is intended for use in the histologic demonstration of nuclear staining. Hematoxylin solutions mordanted with aluminum are routinely used in the histopathology laboratory for nuclear staining. This staining technique is used to make the critical distinction between a normal nucleus and an abnormal one. The traditional formulas for nuclear demonstration using an aluminum mordant are those of Delafield, Harris, Ehrich, Lillie and Mayer. All use aluminum alum (ammonium aluminum sulfate) as the mordant salt. Since the aluminum salts are not in themselves oxidizers, it is necessary to expose the hematoxylin solution to air or chemicals to affect the conversion of hematoxylin to hematein. The aforementioned formulas are also used in special-staining procedures as counterstains for nuclear demonstration. The addition of acid to alum hematoxylin solutions is believed to increase the selectivity of the stain for the nuclei and to counteract the rapid oxidizing effects of chemical oxidizing agents. This latter function enables the solution to maintain some hematoxylin in equilibrium with the hematein to ensure a better stain. Glycerol tends to stabilize the system against over-oxidation and aids in preventing rapid evaporation.