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Hematoxylin & Hematein

Hematoxylin & Hematein

Class: Natural
Ionisation: Acid

Chemical structure of Hematoxylin & Hematein

Common Name: Hematoxylin
Suggested Name: Hematoxylin
Other Names:


C.I. Number: 75290
C.I. Name: Natural black 1
Color: Yellow brown
Solubility Aqueous: 3%
Solubility Ethanol: 3%
Absorption Maximum:
Empirical Formula: C16H14O6
Formula Weight: 302.3


Hematoxylin is a natural dye that is extracted from the heartwood of the tree Haematoxylum campechianum, although histotechnologists are probably more familiar with the name Hematoxylon campechianum. The genus name Hematoxylum is derived from two Greek words: haimatos which means blood, and xylon which means wood.

Hematoxylin is extracted from the heartwood of a bloodwood tree. There may be some differences in method, but one is to chip the heartwood of freshly logged trees, then boil the chips in water. An orange-red solution is obtained, which turns yellow, then black on cooling. The water is evaporated leaving crude hamatoxylin. Depending on the genetic line of the tree, hematoxylin content ranges from 0% - 10%. Further purification is undoubtedly done.

Although it is common practice to use hematoxylin, it is not itself the dye. During the preparation of staining solutions hematoxylin is converted into hematein. This is usually accomplished with chemical oxidizing agents but is sometimes accomplished by atmospheric oxygen over time. Sodium iodate is the most commonly used oxidizing agent for this purpose (0.2g will oxidize 1g hematoxylin). Others are mercuric oxide (now strongly deprecated because it is poisonous), potassium permanganate, and iodine. Hematein may also be referred to as hematoxein, although it is not usually seen in histotechnology references. Hematein is not incorporated directly into most staining solutions because it continues to oxidize in solution and forms non-staining products. The quality of hematoxylin is usually higher and more consistent than the quality of hematein, and solutions made with it are more easily standardized.

The dye is usually used in conjunction with a mordant, the two most common being aluminum (as ammonium or potassium alum), or iron (ferric chloride or iron alum). Other mordants are used much less frequently but include chrome alum and phosphotungstic acid. The tissue component most frequently demonstrated is nuclear chromatin using an aluminum mordant in the Hematoxylin and Eosin general oversight staining method. Using ferric salts as the mordant, it is also used for acid-resistant nuclear staining, the demonstration of muscle striations, and numerous other elements. With phosphotungstic acid, it can demonstrate fibrin, muscle striations, and some neuroglia fibers. There are many published formula.

Due to the widespread use of this dye in medical histology, it is important that a steady supply be available. This has not always been the case. A shortage occurred in the early part of the 1970s. During this period several dyes were tested as substitutes with some success. Unfortunately, none of them have the wide variety of uses that hematoxylin has. Celestine blue B and mordant blue 3 are probably the most successful.

Hematoxylin has not yet been fully synthesized, but the compound has been split into some precursors, which have been successfully re-converted to the original compound.


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