Haematoxylin - also called natural black 1 or C.I. 75290, is a compound Extracted from the bark of the logwood tree. Hematoxylin is a basic and positively charged compound that binds to and forms salts with acidic (basophilic) compounds containing negative charges (such as DNA and RNA, which are acidic/negative because the nucleic acid building blocks that come off the phosphate backbone are negatively charged) and stains them dark blue or violet.
H 1225 (OTTO) Hematoxylin, powder Cas 517-28-2 - used stains in histology. Metal-haematein complexes are used to stain cell nuclei prior to examination under a microscope. Structures that stain with iron- or aluminum-haematein are often called basophilic, even though the mechanism of the staining is different from that of staining with basic dyes.