Chemical analysis of oils, fats, waxes and of the commercial products derived therefrom : founded on Benedikt's second ed. of 'Analyse der fette,' / by Dr. J. Lewkowitsch.

  • Lewkowitsch, J. (Julius), 1857-1913.
Date:
1898
Catalogue details

Licence: Public Domain Mark

Credit: Chemical analysis of oils, fats, waxes and of the commercial products derived therefrom : founded on Benedikt's second ed. of 'Analyse der fette,' / by Dr. J. Lewkowitsch. Source: Wellcome Collection.

    842/872 (page 814)
    which was further confirmed by the numbers furnished by ultimate analysis. The quantitative composition of the product of the interaction of zinc chloride and oleic acid can now be calculated in the following manner:— The constant ether value being identical with the ordinary ether value, anhydrides of the type of acetic anhydride (i.e. anhydrides saponifiable by alkalis and not re-formed on acidifying) are absent. Since the ether value of pure stearolactone (according to theory) is 198*9, the amount of stearolactone in the sample can be calculated from the constant ether value of the sample, viz. 55 T, using the pro- portion 198*9 : 100 :: 55*1 : x; hence cc — 27*7 per cent, or rot. 28 per cent. This number agrees perfectly with that found by direct deter- mination (comp, above). From the iodine value of the sample the proportion of oleic acid— oleic plus isooleic acid—is found. Pure oleic acids absorb, according to theory, 90*07 per cent of iodine; consequently the iodine value, 36, of the sample corresponds to 40 per cent of oleic acids. The true acetyl value of the sample is found by subtracting the constant ether value, 55*1, from the above given acetyl value, 86*1 ; it equals 86*1 - 55*1 = 31*0. From this acetyl value the proportion of /3-hydroxystearic acid, molecular weight = 300, can be found by substituting in the equation (p. 205)— 100. c. M. (M + 42) 56100(M - 42) for c and M, 31 and 300 respectively. Hence x= 21*97, or about 22. The product of the interaction of zinc chloride and oleic acid has, therefore, the following composition :— Per cent. Liquid anhydride . 8 Stearolactone .... • . 28 Oleic acids .... - . 40 /3-Hydroxystearic acid . • 22 Saturated fatty acids (by difference) • 2 100 That there is a small amount of saturated fatty acids (other than hydroxy acids) present may be proved by means of the saponification values in the following manner :— 40 per cent of oleic acid correspond to tlie acid value 79*6 22 ,, ,, /3-liydroxystearic acid ,, ,, 41 *1 120*7 The acid value of the sample having been found = 124*9, the differ- ence, 124*9 - 120*7 = 4*2, must be accounted for by the presence of saturated acids. This conclusion is further supported by the behaviour of oleic acid when heated with zinc chloride to 200° C.