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

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...