Volume 2

Allen's commercial organic analysis : a treatise on the properties, modes of analysis, and proximate analytical examination of the various organica chemicals and products employed in the arts, manufactues, medicine, etc. with concise methods for the detection and estimation of their impurities, adulterations, and products of decomposition.

  • Allen, Alfred Henry, 1847-1904.
Date:
1911-1917
Catalogue details

Licence: Public Domain Mark

Credit: Allen's commercial organic analysis : a treatise on the properties, modes of analysis, and proximate analytical examination of the various organica chemicals and products employed in the arts, manufactues, medicine, etc. with concise methods for the detection and estimation of their impurities, adulterations, and products of decomposition. Source: Wellcome Collection.

    449/540 (page 433)
    J. A. Wilson employs the following process in the presence of soluble fatty acids: 1. The alkali in all forms is estimated by titration with standard acid in the usual manner. 2. Another weighed quantity of the soap is decomposed in an Erlenmeyer flask with a slight excess of dilute sulphuric acid, and the flask kept on the water-bath until the fatty acids separate quite clear. The flask is placed in ice-water to cool and then filtered. The fatty acids are washed 3 times successively with 250 c.c. of boiling water, allowed to cool each time, and filtered. The united filtrates are diluted to 1,000 c.c., and 500 c.c. placed in a beaker and tinted with methyl-orange; N/10 alkali is then run in until the liquid acquires the usual colour, after which a little phenolphthalein is added and the addition of standard alkali continued until a permanent pink is estab¬ lished. The amount used in the latter titration is due to soluble acids and is calculated to caprylic acid. The fatty acids in the flask and that on the filter are dried and weighed, and then dissolved in alcohol and titrated with N/2 alkali. The amount so used, together with that re¬ quired for neutralisation of the soluble acids, deducted from the total alkali, gives the alkali existing in forms other than as soap. If desired, the soap may be decomposed with standard sulphuric acid, methyl-orange added, and the alkali required for neutralisation noted; this, deducted from the total acid used, would give the acid equivalent to the alkali existing in all forms. In this manner are ascertained: Total alkali... Combined alkali. Insoluble fatty acids... Soluble fatty acids. c. Glycerol may exist in soap. In the absence of sugar, it may be estimated with considerable accuracy by the permanganate process. When glycerol is present in considerable amount in soap, Lewkowitsch makes the estimation by dissolving it in water, separating the fatty matter with acid, and filtering off. The filtrate is then neutralised with barium carbonate and boiled down to the consistency of syrup. The residue is then extracted with a mixture of 3 parts of 95% alcohol and 1 part ether, the alcoholic solution filtered and evapo¬ rated on the water-bath to small bulk, and finally dried under a desic¬ cator. The glycerol in the residue may be estimated by the acetin Vol. II.—28