MILK. 83 



FATS. 



The fats of milk are in general those which occur in 

 adipose tissue. There are present also in small quantities 

 fats formed from the volatile fatty acids, particularly butyric 

 and caproic acids. These give to milk-fat (butter) its charac- 

 teristic odor when from any cause the fatty acids are liberated 

 (rancidity). The proportion of the various fats is roughly 

 as follows: triolein, -|; tripalmitin, ^ ; tristearin, ; tributyrin 

 and tricaproin, ^. 



Use the fatty residue in the evaporating-dish (see method 

 of separation). Dissolve the fat in 10 c.c. of ether and add 

 to it 3-5 c.c. of sodium alcoholate. Notice what takes place 

 and compare this saponification with those performed under 

 fats. Evaporate off the ether and replace it with water. 

 The precipitate should dissolve. Now add dilute H 2 S0 4 to 

 a distinct acid reaction. 



Note the odor. To what is it due? Write the equations 

 for the reactions. 



COAGULABLE PROTEIN. 



Lactalbumin and lactglobulin together occur to the 

 extent of 1 per cent in cow's milk. They are closely related 

 to, though not identical with, serum albumin and serum 

 globulin. 



Try three color-protein tests. 



CALCIUM PHOSPHATE. 



In the inorganic salts, phosphoric forms the chief acid 

 and calcium the base, except in human milk, where potas- 

 sium seems to predominate. Strangely enough, iron is only 

 present in traces. 



Dissolve some in dilute HN0 3 . 



