BUTTER 57 



Glycerol-soda. — loo grams of pure sodium hydroxid are 

 dissolved in loo c.c. of distilled water and allowed to stand 

 until clear. 20 c.c. of this solution are mixed with 180 c.c. 

 of pure concentrated glycerol. The mixture can be conveni- 

 ently kept in a capped bottle holding a 10 c.c. pipet, with a 

 wide outlet. 



Sulfuric Acid. — 20 c.c. of pure concentrated sulfuric acid, 

 made up with distilled water to 100 c.c. 



Sodium Hydroxid. — An approximately decinormal, accu- 

 rately standardized, solution of sodium hydroxid. 



Indicator. — Solution of phenolphthalein or methyl-orange. 



A 300 c.c. flask is washed thoroughly, rinsed with alcohol and 

 then with ether, and thoroughly dried by heating in the water- 

 oven. After cooling, it is allowed to stand for about 1 5 minutes 

 •and weighed. (In ordinary operation this preparation of the 

 flask may be omitted.) A pipet, graduated to 5.75 c.c, is 

 heated to about 60° and filled to the mark with the well-mixed 

 fat, which is then run into the flask. After standing for about 

 15 minutes the flask and contents are weighed. 20 c.c. of the 

 glycerol-soda are added and the flask heated over the Bunsen 

 burner. The mixture may foam somewhat; this may be con- 

 trolled, and the operation hastened by shaking the flask. When 

 all the water has been driven off, the liquid will cease to boil, 

 and if the heat and agitation be continued for a few moments, 

 complete saponification will be effected, the mass becoming 

 clear. The whole operation, exclusive of weighing the fat, 

 requires about five minutes. The flask is withdrawn from the 

 heat and the soap dissolved in 135 c.c. of water. The first 

 portions of water should be added drop by drop, and the flask 

 shaken between each addition in order to avoid foaming. 

 When the soap is dissolved, 5 c.c. of the dilute sulfuric acid are 

 added, a piece of pumice dropped in (this must not be omitted), 

 and the liquid distilled until no c.c. have been collected. The 

 condensing tube should be of glass, and the distillation con- 



