316 THE COMPLETE GRAZIER. BOOK n. 



stances that lead to the development of the acids named are discussed 

 at length by Duclaux, but the subject is too technical to be further 

 followed here. The following results of analyses are recorded by the 

 French investigator : 



PERCENTAGE COMPOSITION OF SAMPLES OF (ISIGNY) BUTTER. 



Water . . 12-40 . . 13'36 . . 12'28 



Fat . . . 8671 . . 8o-48 . . 8676 



Milk sugar. . 0'16 . . 0'20 . . 0'17 



Casein and salts . 0'73 . . 0'96 . . 0'79 



100-00 100-00 100-00 



FAT. 



Butyrin . . 5'90 . . 5'87 . . 5'88 



Caproin . 3 '32 3 '40 3 -39 



Other glyeerides . 90'78 . . 90*73 . . 9073 



100-00 100-00 100-00 



Free butyric acid | n . ftQ< , A ., nA ...,,, 



(per 1000 parts) f 



An explanation of the significance of the "iodine number" and of 

 the " viscosity number," as recorded in the table on page 318, is given 

 in the footnote. 1 The table is of interest, as showing that, when 



1 Butter, like other natural fats, is a compound of glycerin with palmitic, oleic, stearic, 

 and other acids. When butter, or other natural fat, is boiled with alkali (potash or soda), 

 the fatty acids and the glycerin are separated from each other, the acids combine with the 

 alkali, forming with it a soap (hence the process is termed saponification), and the glycerin 

 is set free. Soaps thus formed from the fat of milk (butter) may be termed "butter soaps," 

 and it is obvious that such soaps may be produced by the action of either potash or soda. 

 Now, aqueous solutions, containing four or five per cent, of potash soaps, become, when 

 rendered slightly alkaline by the addition of caustic potash, quite viscous, and, when the 

 amount of free alkali (caustic potash) is considerable, are completely gelatinised. Each of 

 the fatty acids, stearic, oleic, &.C., which enter into the composition of fats and oils, forms 

 with potash a soap whose aqueous solution has a definite degree of viscosity, which may be 

 denoted by a number termed the coefficient of viscosity, or the viscocity number ; conse- 

 quently, the determination of the viscocity of soap solutions furnishes a means of dis- 

 criminating between different, fats and oils, and this is especially true in the case of butter 

 and its substances. A soap made from fifteen grams of stearic or oleic acid, with ten grams 

 of caustic potash, dissolved in water, and diluted up to half a litre (0'88 pint) will form, at 

 a temperature of 68, a very viscous solution almost a jelly. Lard, tallow, cotton-seed oil, 

 or olive oil, and all common fats and oils behave similarly, and the same is true of butterine, 

 oleomargarine, and all the commercial substitutes for butter. On the contrary, butter itself 

 when treated in this way gives a limpid solution, the viscocity of which is very slight ; but, 

 on account of the variations in the amount of their volatile acids and olein, butters have 

 nevertheless a very wide range, so that small quantities of foreign fats mixed with butter 

 may escape detection. The volatile fatty acids of butter (butyric, capric, caproic, and 

 caprylic, but chiefly butyric) tend to reduce the viscocity of its- soap solutions, partly on 

 account of their low coefficient of viscocity, and partly on account of their high neutralising 

 power, which leaves less alkali in solution. The determination of the viscocity number is 

 practically effected on the same principle as that of the Nessler test for determining nitrogen 

 in potable waters, namely, a made-up solution is added to till it exactly resembles the 

 solution under trial, and the amount of addition is, of course, known exactly. Hence, the 

 viscocity is determined by means of a solution adjusted to the same viscocity as the one 

 iindtT examination, and the number denoting the viscocity expresses really the number of 

 grams of cane sugar dissolved in water and diluted up to one litre (176 pints) to make the 

 test solution. 



In the New York Dairy Show trials, samples of the butte'- from seven pure-bred 



