The composition of salvarsan / by Robert George Fargher and Frank Lee Pyman.
- Fargher, Robert George.
- Date:
- 1920.]
Licence: Public Domain Mark
Credit: The composition of salvarsan / by Robert George Fargher and Frank Lee Pyman. Source: Wellcome Collection.
6/8 page 375
![Found: Cl = 6*84; S = 5‘l; As = 30*8*; neutralisation value — 15*5.* The combination of a low chlorine content, a high sulphur con¬ tent, and a normal neutralisation value prove the presence of acidic sulphur. It may be pointed out, further, that the product approximates in composition to the monohydrochloride of the mono- sulphamic acid of 3 : 3/-dia,mino-4 : I^dihydroxyarsenobenzene, the formation of which would be expected in view of Bertheim’s state¬ ment (Ghem. Zeit1914, 38, 756) that a mixture of two arsinic acids gives on reduction only the unsymmetrical arsenobenzene. C12H1205N2SAs2,HC1 requires Cl = 7*3; S = 6-6; As = 31*l per cent.; neut. val., 16*6. The remainder of the sulphur is probably attached to arsenic, this mode of combination being indicated by the fact that the distillate from an acid solution of salvarsan often contains traces of hydrogen sulphide, which can be detected by lead acetate and other reagents, whilst 3-amino-4-hydroxyphenylarsenic trisulphide (D.R.-P. 253157) appears to give up at least- part of its sulphur as hydrogen sulphide on boiling with dilute hydrochloric acidr It should be remembered, however, that salvarsan has been shown to- possess- some- of the properties of a colloid (compare Karrer, Ber., 1919, 52, [A], 2319), and it is therefore possible that- a portion of the sulphur unaccounted for by the sulphamo-group may be present in physical association with the compound. The Preparation of 3 : -Diamino-^ : P-dihydroxy arsenoh enzene Dihydrocliloride. During the progress of the foregoing experiments, it became necessary to prepare pure, as distinct from commercial, salvarsan. The reduction of 3 - a m i n o-4 - hy d r oxy ph e ny 1 a r s e n i o u s oxide to the arsenobenzene by means- of sodium amalgam in acetic acid had already been described by Ehrlich and Bertheim (Joe. cit.), and this and several other modifications involving the reduction of 3-nitro4-hydroxyphenylarsinic acid step by step were investigated. The first- series of experiments involved the- preliminary reduc¬ tion of the- nitro-group without affecting the arsinic acid group, leading to 3-amino-4-hydroxyphenylarsinic acid. This had been accomplished by Ehrlich and Bertheim {Joe. cit.) by means of sodium amalgam, and we employed this process until it became * Owing to the small amount of substance available these results are only approximate.](https://iiif.wellcomecollection.org/image/b3062275x_0006.jp2/full/800%2C/0/default.jpg)
