72 



SCIENCE. 



[Vol. XVI. No. 392 



become rancid, when it is clarified by being boiled with 

 dhye, or sour milk, and salt or betel-leaf, and is then kept 

 in closed pots for use It has a peculiar flavor, which is 

 distasteful to Europeans. 



In some parts of Europe the butter is boiled at a gentle 

 heat for a couple of hours, with constant stirring, allowed 

 to cool and settle, and the melted mass is decanted while 

 still liquid into crocks, care being taken not to allow the 

 caseine, or cheesy mass, to intermix. The butter so prepared 

 will keep for a long time without becoming rancid. 



Butter is the best-known of all non-nitrogenous animal 

 foods (fats), but is consumed in very different quantities, 

 varying from the large cupful, as drank before breakfast by 

 the Bedouins near the Red Sea and Persian Gulf, to the thin 

 layer, as eaten at most meals on the slice of bread by the 

 inhabitants of this country. 



Butter is defined by the Oleomargarine Law as the food- 

 product " which is made exclusively from milk or cream, or 

 both, with or without common salt, and with or without ad- 

 ditional coloring-matter." 



Butter is composed principally of butter-fat, with a small 

 and variable quantity of water, caseine or curd, and some 

 salt, which has been added to preserve it and bring out its 

 flavor. 



The following table shows the extremes in composition of 

 numerous samples of butter, as found by various analysts, 

 in regard to their proximate analyses : — 



Tri-stearine, C3H5 (Ci8H3602)3, which occurs in almost 

 every animal and vegetable fat. It may be obtained in a 

 considerable degree of purity in plates of a pearly lustre by 

 repeated crystallizations from ether. It is inodorous, taste- 

 less, neutral, and volatilizing without decomposition under 

 reduced pressure. It is solid at all ordinary temperatures. 

 Its melting-point is from 52° to 69.7° C. (125.6° to 157.4° F.). 



Tri-palmitiue, C3H5 (CieHsiOa^s, which occurs in animal 

 and vegetable fats, and especially in palm-oil, whence its 

 name, and may be obtained by repeated crystallizations from 

 hot ether, in white pearly laminae. The crystals melt at 

 from 46° to 63° C. (114.8° to 143.6° F.). 



Tri-butyrine, C3H5 (0^11703)3, which is found chiefly in 

 butter. At ordinary temperature it is liquid, and has a dis- 

 tinct and peculiar taste and smell. 



Tri-oleine, C3H5 (Ci8H3302)3, which occurs in almost every 

 animal and vegetable fat. It is liquid at all ordinary 

 temperatures, neutral, odorless, and tasteless. 



Wein ' found in butter-fat more or less of the glycerides 

 of palmitic, oleic, stearic, myristic, arachidic, normal cap- 

 rylic, capric, normal caproic, and butyric acids. Glycerides 

 of acetic and formic acids were also found, but not those of 

 propionic, valeric, oenauthylic, or pelargonic acids. The 

 greater part consists of the glycerides of oleic and palmitic 

 acids, that of stearic acid being usually present in smaller 

 quantity. The characteristic constituent of butter-fat is 

 butyrine, which ranges from 5 to 8 per cent. 



Table I. — Extremes in Composition of Numerous Samples of Butters. 



1 European markets. 



> Great Britain. 



What is commonly or commercially known as a simple 

 fat is chemically almost invariably a mixture of several dif- 

 ferent fats, called glycerides; and the name by which they 

 are designated terminates in "ine," e.g., butyrine, stearine, 

 etc. These glycerides are the normal propenyl ethers of the 

 fatty acids, or, in other words, compounds of th« triad alco- 

 hol, glycerine, with the fatty acids. 



Glycerine has the property of uniting with one, two, or 

 three molecules of fatty acid, affording mono-, di-, or tri- 

 glycerides, designated according to the acid. In almost all 

 the natural fats these glycerides occur as trivalent; and in 

 speaking of them the prefix "tri" is generally omitted, 

 being understood. The most commonly occurring glycerides 



Olive and cottonseed oils are composed chiefly of tri-oleine 

 and tri-palmitine. 



Mutton suet consists chiefly of tri-stearine, with small 

 quantities of tri-oleine and tri-palmitine. 



Human fat contains tri-palmitine with some tri-oleine and 

 tri-stearine. 



Beef suet contains the same glycerides and the same quan- 

 tity of tri-oleine as mutton suet, but the percentage of tri- 

 palmitine and tri-stearine is about a mean between the latter 

 fat and human fat (Heintz). 



Lard has more tri-oleine than either beef or mutton suet, 

 and less of the other two glycerides, tri-palmitine and tri- 

 stearine. 



' Sitzungsber. d. Phys. Med. Soc. Erlangen xi., p. 1664. 



