Ultramarine substituted

The isolation and study of triatomic radical anions is also a matter of considerable interest. The ozonide ion has been successfully studied as alkali metal salts in an argon matrix (74) and the S3 ion as a substitutional species in a sodium chloride crystal as host 69,75). The latter species has also been identified by resonance Raman studies as the one responsible for the blue colour of ultramarine blue and lapis lazuli (70). Sulphur also forms deep blue solutions under certain circumstances in many other media (e.g. hexamethylphosphoramide and dimethylformamide), and it is unquestionably the S3 ion which is the species responsible for the colour in these cases also. 

Several derivatives can be made of ultramarine (q.v.) by substituting various constituent elements. In the case of ultramarine violet, ultramarine blue is mixed with about 2.5 5% ammonium chloride, heated to 200-250 C for four days and exposed to air until the purple colour develops alternatively ultramarine can be heated with chlorine and hydrochloric acid (Heaton, 1928 Colour Index, 1971 Buxbaum, 1998). Ultramarine red (q.v.) is produced as a derivative of this pigment. 

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