Volume 1

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

  • Lewkowitsch, J. (Julius), 1857-1913.
Date:
1909
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.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    43/574 (page 19)
    and palmitic acid; (3) tribromohydrin with sodium (or silver) palmitate. It dissolves with very great difficulty in cold alcohol, more easily in hot alcohol; it is also sparingly soluble in cold ether. From hot ether it crystallises in needles, melting at 63°- 64° C. (Chittenden), 65*1° C. (Scheij), 65’5° C. (Guth), and solidify- ing at 45°-47° C. If the crystals are heated to 70° C. and allowed to solidify, they melt a little above 45° C., then solidify again, and finally melt at 65’1° C. The specific gravity is d8ff = 0’8657; the refractive index n8D° = T43807. Tripalmitin occurs in most oils and fats, and is the preponderant constituent of palm oil, Japan wax, and myrtle wax. Tristearin, Stearin, C3H5(0. C18H350)3, is obtained by heating (1) monostearin with 15-20 parts of stearic acid for three hours at 275° C. {Berthelot); (2) glycerol with excess of stearic acid {Scheij)-, (3) distearin with stearic acid {Guth); (4) tribromohydrin and silver or sodium stearate {Partheil and v. Velsen; Guth). Stearin is less soluble in cold alcohol than is palmitin; from solutions of tristearin in boiling alcohol the dissolved substance separates nearly completely on cooling. It dissolves sparingly in cold ether and cold petroleum ether (more readily if the solvents are heated); in benzene and chloro- form it dissolves readily in the cold. The stearin obtained by crystal- lisation from ether melts at 71'6° C., and solidifies at 70° C. to an indistinctly crystalline mass. The crystallised stearin exhibits only one melting point; but when the crystals are heated above this melting point—by at least four degrees—they solidify at about 52° C. to a wax-like substance, melting at 55° C.; on further heating a few degrees above this latter point, the melting point 71’6° C. is again observed. The explanation of this pheno- menon has been given already (p. 14). The specific gravity of a (not quite pure) specimen of stearin in the melted state was found to be 0’9235 at 65*5° C.; Scheij gives d8ff = 0’8621. The refractive index %8D° is T43987 {Scheij). Stearin indicates in the butyro-refractometer 34 “ degrees ” at 55° C., and 23’5-24’5 “ degrees ” at 75° C. {Partheil and v. Velsen-, Guth). It distils unchanged in vacuo. The (partial) conversion of stearin into ethyl stearate by boiling with a solution of sodium in absolute alcohol was first observed by Duffy;1 the same change was noted by Bouis2 on heating stearin with small quantities of alcoholic potash. On substituting amyl alcohol for ethyl alcohol, amyl stearate is obtained (cp. p. 80). Stearin occurs chiefly in solid fats. It is most likely contained therein as a mixed glyceride, for Bomer3 found in beef tallow only 14 per cent and in mutton tallow only 3 per cent of pure stearin. Triarachin, Arachin,4 C3H5(0 . C20H39O)3 [prepared by Berthelot from diarachin and arachidic acid], is very slightly soluble in ether. 1 Journ. Chevn. Soc. 1852, 303. 2 Compt. rend. 45, 35. 3 Zeit. f. Unters. d. Nahrg. u. Genussm. 1907, xiv. 90. 4 It may be pointed out that Moser (Landw. Versuchst. 1904, 321) gave the name ‘ ‘ arachin ” to an alkaloid found by him in the seeds of Arachis hypogcea.