The solubilities of the pharmacopœial organic acids and their salts / by Atherton Seidell.

  • Seidell, Atherton, 1878-1961.
Date:
[1910]
Catalogue details

Licence: In copyright

Credit: The solubilities of the pharmacopœial organic acids and their salts / by Atherton Seidell. Source: Wellcome Collection.

    63/104 (page 61)
    G1 it was found that with both methods the Ihiiits of the conditions within which the reactions ])roceed according to the accepted equa- tions are so narrow that the results obtained under ordinary condi- tions were of uncertain reliability. The details of the exj)eriments which led to this conclusion have been published elsewhere “ and therefore neetl not be given here. In regard to the methods for the determination of the inorganic constituent of the salts it will be noted that the procedures recom- mended by the pharmacopeia vary for each of the three different basic constituents present, viz, for the sodiiun, lithium, and strontiiun salts. In the first case the sami)le is ignited and the asli titrated with standard acid; in the secoiul it is mixed witli anmionium sulphate and ignited in order to convert the lithium to lithium sul])liate; with the last, concentrated sulphuric acid is prescribed as the agent for converting the residue to strontium sulphate. As has been shown in the case of sodium benzoate (p. 28), so also with sodium salicylate has it been found necessary to extract the fii’st ignited residue of the sample with water ami ignite the unburned carbon, adding tlie solu- tion of this second ash to the first in order to have all the sodium in available form for the titration with standard acid. With this pre- caution the pharniacopoeial method for sodium salicylate is entirely satisfactory. Some years ago a method for the determination of salicylates was })roposed by Barthe,'' according to which an excess of hydrochloric acid was adtled to the aqueous solution of the sample of salicylate and the mixture evaporated to dryness at not over 50°. The residue, consisting of free salicylic acid ami the chloride of the base, was then titrated with standard alkali, using phenolphthaloine as indicatoi-, and subsequently the chloride was titrated with standard silver nitrate solution. In view of the experiments of h^i-esenius and Grunhut,^^ who found that satisfactoiy results for salicylic acid could not be obtained by any method of liberating salicylic acid, shaking out with volatile solvents and evaporating at a very low temperature, it did ajq)ear advisable to attempt the determination of salicylic acid as suggested by Barthe, but it was believetl that the determination of the base by titration of the chloride might yield good results. Ex])eriments along this line were therefore made, including, however, a modification for removing as much as possible of the free salicylic acirl before titrating the chloride. The following results were obtained upon a sample of sodium salicylate which contained 100.2 per cent CfiIl40IlC00Na on the basis of the determination made by the })hannaco|)oeial method modified as above mentioned. 50 grams were dissolved in water and o Seidell, J. Am. Chem. Soc., 31, 1168-77. 1909. b Bull. 800. ohim., (3) 11, 517, 1894.