242 
WILLIAM J. ROBBINS 
alcohol acidified with i cc. of HCl (sp. gr. 1.18-1.19), and in alcohol 
acidified with i cc. of acid one third of this strength, were identical. 
From a consideration of the preceding data it would seem that the 
precipitation of starch and dextrins in 73 percent acid alcohol is a 
method that can be used with considerable satisfaction for the deter- 
mination of diastatic action. 
Preparation of Cultures and Use of the Alcoholic Precipitation 
Method for Determining Digestion. — The culture solutions in which 
single salts were used were prepared as follows : One liter of a solution 
103 
— 1 
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. 60 
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■ Time in Minutej ■ 
Fig. 3. 
of M/ioo concentration of the salt to be tested was prepared, and a 
stock solution of 1.6 percent soluble starch was also prepared by 
heating in an autoclav at a pressure of 15 pounds. The various con- 
centrations of the salt — M/iooo, M/io,ooo, etc. — were made by 
diluting the original salt solution and mixing with the starch solution 
so that the starch content of each series was approximately constant. 
Each culture contained 50 cc. of solution in an Erlenmeyer flask of 
125 cc. capacity. The cultures were sterilized in an autoclav at 15 
