There is much more phosphotungstic acid in the solution than hematein.

The phosphotungstic acid binds all of the available hematein to form a blue lake pigment.

The pigments hematoxylin and hematein can be extracted and are complex phenols similar to bioflavonoids.

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

In acidic solutions, complexes of hematein with metals (usually aluminium or iron, but also chromium, zirconium and several others) are used as biological stains.

The staining method involves application of hemalum, which is a complex formed from aluminum ions and hematein, which is an oxidation product of haematoxylin.

Hematein exhibits indicator-like properties, being blue and less soluble in aqueous alkaline conditions, and red and more soluble in alcoholic acidic conditions.

There is evidence to indicate that coordinate bonds, similar to those that hold aluminum and hematein together, bind the hemalum complex to DNA and to carboxy groups of proteins in the nuclear chromatin.