78 MILK PRODUCTS 



Acid Mercuric lodid. — Mercuric chlorid, 1.35 

 grams; potassium iodid, 3.32 grams; glacial acetic 

 acid, 2 c.c. ; water, 64 c.c. 



Alumina-cream. — ^A cold saturated solution of 

 alum is divided into two unequal portions, a 

 slight excess of ammonium hydroxid is added 

 to the larger portion and the remainder added 

 until a faintly acid reaction to litmus is obtained. 



The entire contents of the can are transferred 

 to a porcelain dish and thoroughly mixed. A 

 number of portions of about 25 grams are 

 weighed carefully in 100 c.c. flasks. Water is 

 added to two of the portions, and the solutions 

 boiled. The flasks are then cooled, clarified by 

 means of a small amount of the acid mercuric 

 iodid and alumina cream, made up to mark, 

 filtered, and the polarimetric reading noted. 

 Other portions of the milk are heated in the 

 water-bath to 55°; one-half of a cake of com- 

 pressed yeast is added to each flask and the 

 temperature maintained at 55° for five hours. 

 Acid mercuric iodid and alumina-cream are 

 then added, the solution cooled to room tem- 

 perature, made up to mark, mixed, filtered, and 

 polarized. The amount of sucrose is determined 

 by formula given above. Correction for the 

 volume of precipitated solids may be made by the 

 double-dilution method. The total reducing 

 sugar is estimated in one of the portions by one of 



