Metal Complexes of Alizarin IV—The Structure of the Potassium and Calcium Salts of Alizarin and of 3‐Nitroalizarin

The preparation of the potassium and calcium salts of alizarin and of 3‐nitroalizarin is described. Their structures have been established and compared with those of salts of complex alizarates containing the same metals, which have been described in the preceding parts of this series. It was already known that, prior to complex formation, salt formation must take place. With the knowledge of the structure of these salts, the mechanism of...