Chemical Analysis of Milk and its Products. 221 



this amount, and the flask when cool is weighed again. 

 10 cc. of 95 per cent, -alcohol and 2 cc. of a concentrated 

 soda solution (1:1) are then added to the flask which is 

 securely stoppered with a cork stopper tied down with a 

 piece of twine. The flask is heated for an hour on the 

 water bath, being gently rotated from time to time in 

 order to facilitate the saponification. The flask is then 

 uncorked, the alcohol evaporated slowly and the heating 

 continued until the last traces of alcohol are gone. 



100 cc. of recently boiled distilled water are now added, 

 and the flask heated on the water bath until the soap 

 formed is completely dissolved. When cooled to about 

 70 C., 40 cc. of dilute sulfuric acid (25 cc. cone. H 2 SO 4 

 per liter) are added to the soap solution to decompose 

 the soap into free fatty acids and glycerol. The flask is 

 restoppered and heated until the insoluble fatty acids 

 separated out form a clear oily layer on the surface of 

 the acid solution in the flask. After cooling to room 

 temperature, a few pieces of pumice stone (prepared by 

 throwing the pieces at a white heat into distilled water 

 and keeping them under water until used) are added, 

 the flask connected with a glass condenser, heated slowly 

 till boiling begins, and the contents then distilled at such 

 a rate as will bring 110 cc. of the distillate over in as 

 nearly thirty minutes as possible. 



The distillate is mixed thoroughly and filtered through 

 a dry filter; 100 cc. of the filtrate are poured into a 250 cc. 

 beaker and titrated with a deci-normal barium -hydrate 

 solution, half a cubic centimeter of phenolphtalein solu- 

 tion being used as an indicator. A blank test is made 

 in the same manner as described, and the amount of 



