1:3-Benzodiazolearsinic acids and their reduction products : by Robert Reginald Baxter and Robert George Fargher.

  • Baxter, Robert Reginald.
Date:
1919.]
Catalogue details

Licence: Public Domain Mark

Credit: 1:3-Benzodiazolearsinic acids and their reduction products : by Robert Reginald Baxter and Robert George Fargher. Source: Wellcome Collection.

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    to handle, and consequently the reduction was carried out by means of sodium hyposulphite. This gives pale yellow arsenobenzenes, insoluble in water, which were converted into hydrochlorides by precipitating their solutions in acetic acid with excess of hydro¬ chloric acid, or by treating the suspensions of the bases in water with just sufficient hydrochloric acid to bring about solution, and precipitating as before. The hydrochlorides form pale yellow powders, soluble in water, but very sparingly so in the usual organic solvents. Their aqueous solutions react strongly acid to litmus, but neutral to methyl-orange. It was expected that this acidity would prove too great for pur¬ poses of intravenous injection, and that it would be difficult to distinguish between the effect due to the acidity and that due to the arsenic compound. This was confirmed by experiments with 5 : b'-arseno-l : 3 : V: V-benzodiazole (VIII) by Miss Soref, of the Wellcome Physiological Research Laboratories. Experimental. 3 :4-Diamino yhenylarsinic A cid. The preparation of considerable quantities of this acid was carried out according to the directions given by Bertheim (loc. cit.), save that it was found advisable to omit the boiling of the solution after the reduction with sodium hyposulphite, as this diminished the yield and gave a more highly coloured product. 1 : 3-BenzodiazoIe-5-arsinic Acid (V). Ten grams of 3 :4-diaminophenylarsinic acid were boiled under a reflux condenser for six hours with 100 c.c. of glacial formic acid. After removal of the excess of formic acid by distillation, water was added, when 7*5 grams of crystalline material rapidly separated. To remove adhering traces of colouring matter, the product was treated with charcoal in dilute alkaline solution. On making neutral to methyl-orange, crystallisation commenced at once, practically the whole being recovered in a pure state. 1 :3-Benzodiazole-5-arsinic acid crystallises from water, in which it is sparingly soluble, in clusters of minute, flattened prisms, which are anhydrous. On heating, it gradually darkens above 250° and decomposes rapidly about 297° (corr.). Found: N = 11*4; As = 30’8. C7H703N2As (242T) requires N = 11‘6; As —30-96 per cent.
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