EXAMINATION OF ADIPOSE TISSUE. 143 



the assumption of the elements of water, into fatty acids, 

 which combine with the alkalies to form soaps and glycerin; 

 for example, 



C 5I H 98 6 + 3H 2 = 3(C 16 H 32 2 ) + C 3 H 8 O 3 . 



Tripalmitin Water Palmitic Acid Glycerin 



Process of Saponification. 



Weigh off about 15 g. of caustic potash in an evaporating- 

 dish, add 10 cc. of water, and heat on the water-bath until 

 the caustic potash has dissolved. At the same time make up 

 100 cc. of 90 per cent, (volume per cent.) alcohol in a measur- 

 ing-cylinder. Pour the caustic potash solution into a 400-cc. 

 flask and rinse out the dish with a part of the alcohol. Then 

 weigh off 50 g. of lard in an e vapor ating-dish, place the dish 

 on the water-bath, heat till the fat is completely melted, pour 

 the melted fat into the same flask, wash out the fat remaining 

 in the dish by heating with portions of the alcohol on the 

 water-bath, and finally pour the rest of the alcohol into the 

 flask. Place the flask on a hot-water bath, heat, and cau- 

 tiously shake the contents thoroughly as soon as the alcohol 

 begins to boil. Saponification takes place very quickly, 

 almost immediately. 1 In order to determine with certainty 

 whether the Saponification is completed, pour a small quan- 

 tity of the alcoholic fluid into a little distilled water: the solu- 

 tion must be clear; it should contain no unsaponified fat in 

 the form of drops of oil. The solution will then contain soap 

 and glycerin besides the excess of caustic potash and the 

 alcohol. 



Separation of the Fatty Acids and the Glycerin. 



Pour the contents of the flask gradually and with con- 

 stant stirring into hot dilute sulphuric acid contained in a 



1 If we heat the alcoholic solutions of the fat and caustic potash to 

 boiling separately and pour the two solutions together, Saponification 

 does take place at once on shaking. 



