Preparation of a soluble ferric arsenate / by Frederick B. Power and Harold Rogerson.

  • Frederick Belding Power
Date:
[1908?]
Catalogue details

Licence: In copyright

Credit: Preparation of a soluble ferric arsenate / by Frederick B. Power and Harold Rogerson. Source: Wellcome Collection.

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    salts required for the reaction may be considered to be those represented by the following equation :— Na2HAs04 + Fe' C6H507 = Fe' As04 + Na2HC6H507. 186 245 (100) (131-7) One hundred parts of anhydrous sodium arsenate would thus require such an amount of iron as would correspond to 131 7 parts of anhydrous ferric citrate. It has been found, however, that the scaling of the product is much facilitated if one-tenth more than the calculated amount of ferric citrate is employed, and the proportion of the latter salt would thus be practically 145 parts. It is likewise important that an¬ hydrous sodium arsenate should be used in this process, on account of the variable amount of water contained in the crystallised salt. The method of procedure is briefly as follows : — To an amount of solution of ferric citrate corresponding to 145 parts of the anhydrous salt is added 100 parts of anhy¬ drous sodium arsenate, and the mixture gently heated on a water-bath until the latter salt has become completely dis¬ solved. The original brown colour of the liquid will then have changed to a bright green. The liquid is subsequently filtered, evaporated at a gentle heat to a syrupy consistence, and spread on plates of glass, so that, on drying, the salt may be obtained in the form of scales. Soluble Iron Arsenate2 (Terri Arsenas Solubilis), as thus prepared, has the following characters, which will serve for its identification. Thin, bright green, transparent scales, which are readily and completely soluble in water, affording a bright green solu- 2 The designation “Soluble Iron Arsenate” has, unfortunately, been adopted by the ‘British Pharmaceutical Codex,’ p. 427, as a synonym for a preparation to which the same work has given the evidently incorrect title of “ Ferri Citro-Arsenias Ammoniatas (Ammoniated Citro-arsenate of Iron).” It is described as follows:—“ Ammoniated citro-arsenate of iron is said to be a double salt of ferrous arsenate and ammonium citrate. It occurs in green or yellowish-green deliquescent scales, very soluble in water. It contains from 15 to 18 per cent, of metallic iron, and the equiva¬ lent of 14 per cent, of arsenious anhydride.” A preparation which is stated to contain the amount of iron and arsenious anhydride above indi¬ cated, and which evidently corresponds with that described in the B.P.C., has been in use for some time, but it is designated by the manufacturers as “Iron Arsenite with Ammonium Citrate (Ferrous Arsenite with Ammo¬ nium Citrate).” The synonym, “Soluble Iron Arsenate,” which has been adopted by the ‘ British Pharmaceutical Codex ’ for the preparation described in that work is, therefore, evidently a misnomer.