SUBJECTS ferrous compounds

An acid of sp. gr. 1-517 at 15°/4° absorbs 0-88 per cent, of nitric oxide so that the coefi. of absorption is 12-5. The speed of absorption varies with the cone, of the acid. C. A. Winkler obtained no absorption of nitric oxide by the hydrate of sulphuric acid and M. Berthelot said that nitric oxide is very slightly soluble in cone, sulphuric acid. O. Lubarsch made some observations on this subject. E. Desbassayns de Richemont said that if the sulphuric acid contains a little ferrous sulphate, nitric oxide imparts to it a red colour and if copper sulphate, a violet colour. In the latter case, W. Manchot found that the coloration is due to the formation of an easily dissociated copper nitrosylsulphate, CuSO4.NO— vide infra. For the corresponding compound with ferrous sulphate, vide infra. G. Lunge found that 1 c.c. of sulphuric acid of sp. gr. 1-84 absorbs 0-035 c.c. of nitric oxide, and an acid of sp. gr. 1-50, 0-017 c.c. and O. F. Tower, v vol. of nitric oxide at 760 mm. absorbed by one vol. of acid 18° and H2S04 per cent. 

In 1928, at Grangemouth, Scotland, at the works of Messrs. Scottish Dyes Ltd., traces of a dark blue insoluble complex were noticed in the iron vessels used to prepare phthalimide from phthalic anhydride and ammonia (65, 221). This product was subsequently shown to be ferrous phthalo-cyanine. Since then literally thousands of patents and publications concerning the phthalocyanines have appeared. It is probable that the phthalocyanines have been the subject of more physical studies than any other single class of compound, partly as a result of their unique structure and partly because of their high thermal and chemical stability. 

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