Hematoxylin is a naturally occurring stain extracted from the logwood tree. For use in staining, the hematoxylin is oxidized to hematein which combines with the trivalent mordant and is the active staining ingredient. The usual mordants for cytology are aluminum salts. Mayer’s hematoxylin is a solution of aluminum ammonium sulfate, acetic acid and hematoxylin in water. It is commonly used as a nuclear stain in cytology and the counterstains are EA and OG stains. It is usually used progressively. This item is manufactured in the United States by Medical Chemical Corp. Medical Chemical corp.