Volume 1

Chemical technology and analysis of oils, fats, and waxes / by J. Lewkowitsch.

  • Lewkowitsch, J. (Julius), 1857-1913.
Date:
1904
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Chemical technology and analysis of oils, fats, and waxes / by J. Lewkowitsch. Source: Wellcome Collection.

    28/454 (page 8)
    CHAP. CLASSIFICATION OF OILS, FATS, AND WAXES glycerides. In the former class only one representative can exist for each fatty acid, namely, 0. R C3H50. R 0. R, whereas in the second class two isomeric triglycerides may be expected in the case of two different acid radicles, and three iso- merides in the case of all three acid radicles being different, as explained by the following formulae :— 0• R] 0. Ro 0. Ri O.R„ O.R, C3H5 O.R,; C3H5 O.R,; C3H5 0 . R„; C3H5 0 . R,; C3H5 0 . Rs 0 - R> O.R2 O.R3 0. Ra O.R,. Until recently most of the natural fats were considered to be mixtures of simple triglycerides of the several fatty acids, say of tripalmitin, tristearin, and triolein, these being the most frequently occurring triglycerides. In favour of this assumption it was main- tained that on cooling liquid fats, tripalmitin and tristearin separated out either in their pure state or as a mixture. The theoretical postulate, that there should be in existence also mixed glycerides, had up to lately obtained but very slender support through the experiments of Bell and Lewin (see “Butter Fat,” chap, xiv.), who stated that in cow butter probably oleopalmito-butyrate, of the formula C3H5(0. C18H:i30)(0. C16H8I0)(0. C4H70), occurred. But since Heise1 discovered oleodistearin in Mkanyi fat and in kokum butter, other experimenters have isolated a consider- able number of mixed triglycerides from natural fats. The preparation of pure triglycerides from natural products is a very laborious task, and has not always been accomplished satis- factorily, owing to the great difficulty of separating the various triglycerides. Hence, for the preparation of pure triglycerides, synthetical methods must be employed. (See Appendix.) The pure triglycerides were first obtained by Berthelot on heating glycerol with fatty acids. As has been explained already, mono- glycerides and diglycerides are formed simultaneously. In order to exclude the formation of the latter, Scheij'2 heated glycerol with an excess of fatty acid, and with a view to obtaining complete esterifi- cation by removing the resulting water, a slow current of air was passed through the reacting mass. In the case of the triglycerides of the lower acids, a small quantity of fatty acids distils over simultaneously with the water, and it is therefore necessary to add, from time to time, a fresh quantity of acid to the mixture of glycerol and fatty acid. In the case of the higher fatty acids, the com- pletion of the reaction is indicated by the cessation of the evolution of water. The pure glycerides may also be prepared by heating together 1 Arbciten ecus dem Kaiscrlichen Oesundheitsamle, 1896, xii. 540 ; xiii. 302. * lice. d. Irav. chim. d. Pays-Has, 18, 169.