Nuclear chemistry

Metal

Biology

Calcium

Molecule

Inorganic chemistry

Genetics

Organic chemistry

Staining

Medicine

Chemistry

ALIZARIN RED

Alizarin

Infrared spectroscopy

Aluminium

Hydrate

Pathology

Journal of the Society of Dyers and Colourists

We had reason to doubt the correctness of current opinion that the formula of the calcium–aluminium lake of alizarin (Turkey Red) is Ca 2 A1 3 Az 4 (where Az represents an alizarin molecule minus two hydroxylic hydrogen atoms). We therefore carried out a further study of this complex, the results of which are presented in this paper. The molecular structure of the complex has been established. The complex has been prepared in vitro and purified by washing, crystallisation, and chromatographic separation. The structure has been elucidated by conventional analytical methods, including infrared spectroscopy. The basic compound has been established to be CaAl(OH)(Az) z , in which calcium is bound as an ion and aluminium forms part of a chelate ring with the 9‐carboxyl and 1‐hydroxyl groups of alizarin. This compound can take up three molecules of water, forming a new compound in which the water molecules are part of the molecular lattice. This new compound can form a hydrate with another three molecules of water.

Metal Complexes of Alizarin I—The Structure of the Calcium–Aluminium Lake of Alizarin