The chemical character of so-called iodo-tannin compounds / by Frederick B. Power and Frank Shedden.

  • Power, Frederick B. (Frederick Belding), 1853-1927
Date:
[1901]
Catalogue details

Licence: In copyright

Credit: The chemical character of so-called iodo-tannin compounds / by Frederick B. Power and Frank Shedden. Source: Wellcome Collection.

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    in<r an additional quantity of iodine, and the highly coloured solution then possesses the odour of iodine. In eider to ascertain the nature of the combination formed by the tannin and iodine, Socquet and Guilliermond conducted the following simple experiments : — (1) With a solution of lime a precipitate of calcium tannate was obtained, whilst the iodine remained in solution as calcium iodide. (2) With gelatin a precipitate was obtained which, when thoroughly washed with water, was found to contain no iodine the latter remaining entirely in the solution in a state of com¬ bination, although accompanied by some tannate of gelatin, which was difficult to separate. (3) With lead acetate a precipitate of lead iodide was first ob¬ tained, and subsequently lead tannate was precipitated. (4) On e\ aporating the iodo-tannin solution no free iodine was developed until it approached the point of dryness. A similar result was obtained on distilling a large volume of the solution, v hen a purely aqueous distillate was obtained, and a strongly acid solution, containing no free iodine, was left in the retort * I loin these results they arrived at the following conclusions :_ lh.it during the contact of the water, iodine, and tannin, a portion of the water becomes decomposed ; that hydriodic acid is ioimed, and that a portion of the tannin is transformed bjr oxida¬ tion into a particular tannin which is less soluble than ordinary tannin, and that the unaltered tannin forms, with hydriodic acid, a soluble and stable combination which even distillation is not able to change. iho same authors finally proposed a formula for an iodo-tannin syrup, and recommended extract of rhatany to be used for this purpose in place of gallo-tannic acid, on account of the disagree¬ able astringency of the latter. Barnouvin (Rep. de Pharm., 1892, p. 350, and Proc. Amer Pharm. Assoc., 1893, vol. 41, pp. 578, 775), in a paper entitled Composes iodo-tanniques,” has described a so-called “ iodo- tannm compound which he prepared by adding iodine to tannin in such a proportion that after standing for an hour or two it no longer gave a reaction for free iodine with starch. It was then evaporated to a syrupy consistence, spread on glass, and thas obtained in yellowish-brown scales, which were soluble in water and in alcohol. No statement is made in the paper respecting the amount of iodine contained in this preparation, nor does it ap¬ pear to have been.ascertained that it actually contained iodine j