50 MILK SuPPLY 
tory, provided that the alkaline solutions used are correct. This 
work involves considerable expense, however, and unless the 
solution is carefully prepared and made up fresh often, its use 
may yield misleading results. Again, when the acid test is per- 
formed on the milk of each can, the acceptance or rejection of 
the milk depends altogether on the per cent of acid it contains. 
Although milk may be otherwise unfit for use, it will pass, as 
long as it is low in acidity. Experience has shown that, while 
it is necessary for the condensery to decide on a maximum acid- 
ity of milk above which all milk be rejected, the nose and the 
palate of the experienced inspector are better criterions tnan 
the acid test alone, as tothe fitness of milk for condensing. Acid 
tests are valuable in the case of, uncertainty and suspicion as 
to the quality of any given can of milk. All milk containing .18 
per cent lactic acid or more is dangerous for condensing pur- 
poses. 
Acid Test for Daily Use, Where Each Can of Milk is Tested. 
Stock Solution——Weigh out two hundred grams of sodium 
hydrate C. P. and add distilled water to make up one liter. 
Keep tightly stoppered. 
Solution for Daily Use-—Mix 4 c.c. of stock solution with 
991 c.c. of distilled water, and add 5 c.c. of phenolphthalein indi- 
cator. he indicator is prepared as follows: dissolve one gram 
of dry phenolphthalein in 100 c.c. of 50 per cent alcofol. Each 
cubic centimeter of the prepared alkaline solution neutralizes 
Ol per cent lactic acid, 18 ¢.c. of the prepared solution, there- 
fore, neutralize .18 per cent lactic acid, when a 17.6 c.c. pipette 
is used for measuring out the milk. 
Making the Test—With the Babcock pipette, measure 17.6 
c.c. into a white cup. With a small dipper, holding exactly 18 
c.c., pour 18 c.c. of the prepared solution into the cup; stir or 
shake. If the mixture remains faintly pink, it contains less than 
18 per cent acid and will pass; if it turns white, it contains more 
than .18 per cent acid and should be rejected or subjected to addi- 
tional tests. 
The stock solution should be standardized by a chemist. 
The prepared solution should be made up daily. Both solutions 
