Elements of human physiology / by L. Hermann ; translated from the sixth edition by Arthur Gamgee.

  • Gamgee Arthur, 1841-1909.
Date:
1878
Catalogue details

Licence: Public Domain Mark

Credit: Elements of human physiology / by L. Hermann ; translated from the sixth edition by Arthur Gamgee. 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.

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    following are contained in milk, and constitute the fat of butter: myristin, caprinin, caprylin, capronin, butyrin. The neutral fats are fluid (oils) or easily melted, insoluble in water, easily soluble in ether and alcohol; when fluid they render paper transparent (cause grease spots) ; when mixed with colloid substances and water, they admit of being broken up into fine drops, so that the fluid becomes white and opaque (emulsion). Under the influence of hydrolytic ferments, or when superheated with water, they combine with the elements of water, glycerin and free fat acids being liberated ; thus :— C3H,(O0,eH3,O)3 + 3H,0 = 03H,(OH)3 + 3(C,eH3,0(OH)) Tripalmitiu Water Glycerui Palmitic acid The rancid smell of decomposing fats is due to volatile acids, which happen to be formed under the circumstances. When the neutral fats are boiled with solutions of the alka- line hydrates or carbonates, they undergo the process of saponifi- cation, i.e. they combine with the elements of water, and decom- pose into glycerin and a fatty acid; the latter constituent combining at once with the alkaline metal to form a soluble salt. Thus when stearin, palmitin, or olein are boiled with potash hydrate, or with sodium hydrate, we have as results of the opera- tion in the first case potassium stearate, palmitate, or oleate, respectively, and glycerin ; in the second case there result sodium stearate, palmitate, or oleate, and glycerin. When boiled with litharge the neutral fats yield an insoluble lead compound and glycerin. The term soap is applied to the metallic salts of the fatty acids, and hence the term saponification is employed to designate the process which results in the formation of these compounds. The following are some of the more important characters of the three principal neutral fats occurring in the animal body:— Stearin, or Tristearin, C3Hg(Ci8H3gO)303, is the chief con- stituent of the more solid fats. Its melting point is higher than that of any other neutral fat, but varies, according to the treatment to which it has been subjected, between 53° and 66°. It is insoluble in water, but is soluble in hot alcohol, in ether and chloroform. It separates from its solution in hot alcohol in the form of shining rectangular scales. Palmitin, or Tripalmitiu, C3H5(C,gH3jO)303, always accom- panies stearin in the animal fats. Its melting point is like that of stearin, not very constant, varying with the treatment it has undergone, but is certainly lower than that of stearin. The mean melting point is about 45° C. Palmitin is insoluble in water ; it is more readily soluble in hot alcohol than stearin; it is deposited from its alcoholic solution in the form of needles. Alcoholic solutions of mixtures of stearin and palmitin