GB412366A - Improved processes for making compounds containing heavy metals and sulphhydryl groups from keratinates - Google Patents

Abstract

Heavy metal compounds of mercaptokeratinates which are useful therapeutically are prepared by first forming the zinc compounds, then decomposing them with hydrogen sulphide, and finally treating the resulting mercaptokeratinic acids with compounds of heavy metals. The zinc compounds are obtained by hydrolyzing materials containing keratin with acid in excess until a jelly is produced, e.g. by the process described in Specification 370,295, reducing the product by addition of zinc, and neutralizing to precipitate the zinc compounds. As heavy metals are mentioned silver, gold, mercury, copper, lead, antimony, arsenic and bismuth, and their compounds include organo arsenic and antimony compounds. Before adding arsenic, antimony or bismuth compounds, the combining capacity of the mercaptokeratinic acid may be estimated by titration with silver nitrate until no further reaction occurs with sodium nitroprusside. In the case of the preparation of the gold compound, the keratinic acid solution may first be saturated with sulphurous acid. According to the examples, (1) hair is treated with 20 per cent hydrochloric acid until converted into a gelatinous mass, zinc dust added in portions, and the zinc compound precipitated by neutralization with soda lye; (2) the keratinate prepared according to the process of Specification 370,295 is dissolved in hydrochloric acid, zinc added and the product neutralized; (3) hydrogen sulphide is passed into an p aqueous suspension of the zinc compound of (1) or (2), the zinc sulphide filtered off, and the mercaptokeratinic acid isolated by evaporation in vacuo; (4) the acid of (3) is treated in aqueous solution with sodium aurichloride, silver nitrate, mercury acetate, copper acetate, lead acetate, sodium arsenite, potassium pyroantimonate, potassium antimonyl tartrate, bismuth ammonium citrate, gold trichloride (in the presence of sulphur dioxide), p-acetylaminophenylarsonic acid, p-acetylaminophenylarsine oxide, bismuth ammonium citrate, bismuth tartrate or bismuth nitrate, to give the corresponding heavy metal compound which either settles out or is precipitated by the addition of an organic agent, e.g. methyl or ethyl alcohol. Specification 357,189 also is referred to. The Specification as open to inspection under Sect. 91 describes also the preparation of any of the heavy metal compounds after first determining the combining capacity of the acid and contains a further example of the treatment of the above mercapto-keratinic acid with gold trichloride in the absence of sulphur dioxide. This subject-matter does not appear in the Specification as accepted.