haematein

Dissolved haematein slowly reacts with atmospheric oxygen, yielding products that are not useful.

The unmordanted haematein may be responsible for the yellow color imparted to glycogen.

Hematein (US spelling) or haematein is an oxidized derivative of haematoxylin, used in staining.

In the Colour Index (but nowhere else), haematein is called haematine, a confusing word that wrongly implies that the compound is an amine.

This is not to be confused with haematein, which is a dark purple water-insoluble crystalline substance obtained from logwood and used as an indicator and biological stain.

He has also published important investigations on Resorcylic Acid and its derivatives, on haematein and brazilein, on Kamala, purpurogallin, etc, etc."

When oxidized it forms haematein, a compound that forms strongly coloured complexes with certain metal ions, the most notable ones being Fe(III) and Al(III) salts.

The name haemalum is preferable to "haematoxylin" for these solutions because haematein, a product of oxidation of haematoxylin, is the compound that combines with aluminium ions to form the active dye-metal complex.