50 INTRODUCTORY — THE CONSTITUENTS OF MILK. 



heating cholesterol with benzoic acid under pressure, and melts 

 at 150° to 151° C. 



The most characteristic reaction is the following, due to Sal- 

 kowski : — About 10 milligrammes of cholesterol are dissolved 

 in 2 c.c. of chloroform, and the solution shaken with an equal 

 measure of strong sulphuric acid in a corked test tube. The 

 chloroform layer becomes blood-red, passing to cherry-red and 

 purple, the last colour being permanent for several days. The 

 sulphuric acid acquires a well-marked green fluorescence. If the 

 test tube be not corked, or if the chloroform solution be poured 

 into a basin, the colour changes to blue, green, and, finally, yellow, 

 probably due to moisture. On addition of water the solution 

 becomes paler, then blue, and, finally, nearly colourless, while 

 showing a fine green fluorescence. 



By cautiously heating cholesterol with a drop of strong nitric 

 acid and adding ammonia before the product has cooled com- 

 pletely, a yellowish-red coloration is produced. 



If a mixture of 3 measures of concentrated hydrochloric acid 

 and 1 of a solution of ferric chloride be evaporated with a little 

 cholesterol, a reddish-violet coloration changing to blue is pro- 

 duced. By substituting sulphuric acid for hydrochloric acid, 

 a carmine colour is produced, passing gradually to violet, which 

 is changed to scarlet on treatment with ammonia. 



Fatty Acids. 



Acids of tlie Series, C„H2„+iC00H. — As far as is known, only 

 the normal acids of this series, in which n is an odd number, 

 occur in the fat of milk. 



Butyric Acid, CHgCH^CHoCOOH.— Grunzweig has proved 

 that the but3T?ic acid of the fat of milk is normal. This acid is 

 a liquid with a characteristic smell, which is specially developed 

 in dilute solution ; the anhydrous acid has a sharp acid smell, 

 the characteristic smell being hardly perceptible. 



The acid solidifies at — 19° C. The solidified acid melts at 

 —2° to +2° C. according to Linnemann, and at —4-5° to —2° C. 

 according to Zander. The boiling point is variously stated 

 according to difl'erent authorities. Thus — 



Liunemann gives .... _ 162'3° C 



Lieben and Rossi, . 163"2° 



Kahlbaum, . . . . ' 161-5° 



5™!j'' • • ■ ■ lei-s'-iea-s" 



/ianaer, . . . ^ 162'^° 



The author finds \ 161-5°-162'5° 



20° 

 The density is given as 0-9587 at -^ by Bruhl, 0-9746 at 0° 



by Zander, and 0-9886 at 0° by Linnemann. 



