238 Testing Milk and Its Products. 



deliver this amount, and the flask when cool is weighed 

 again. 20 cc. of a glycerol-soda solution (20 cc. of 

 soda solution (1:1) fo 180 cc. of pure glycerol), are then 

 added to the flask and the flask is heated over a naked 

 flame or hot asbestos plate until complete saponification 

 has taken place, as shown by the mixture becoming per- 

 fectly clear. If foaming occur, the flask is shaken 

 gently. 



135 cc. of recently-boiled distilled water are now 

 added, drop by drop, at first, to prevent foaming, and 

 when the solution is clear, cooled to about 70 C. ; 5 cc. 

 of dilute sulfuric acid (200 cc. cone. H 2 SO 4 per liter) are 

 added to the soap solution to decompose the soap into 

 free fatty acids and glycerol. A few pieces of pumice 

 stone (prepared by throwing the pieces at white heat 

 into distilled water and keeping them under water until 

 used) are added, the flask connected with a glass con- 

 denser, heated slowly till boiling begins, and the con- 

 tents then distilled at such a rate as will bring 110 cc. 

 of the distillate over in as nearly thirty minutes as pos- 

 sible. 



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 phe- 

 nolphtalein solution being used as an indicator. A blank 

 test is made in the same manner as described, and the 

 amount of alkali solution used deducted from the re- 

 sults obtained with the samples analyzed. The number 

 of cubic centimeters of barium-hydrate solution used is 

 increased by one-tenth, and the so-called Reichert or 

 Reichert-Meissl number thus obtained. 



