340 REPORT OF THE CHEMIST OF THE 
number of cubic centimeters of standard alkali required to 
neutralize a given amount of acid by 1,000 and divide the 
result by the number of cubic centimeters of acid used in 
titration. Of course, a smaller amount than a liter may be 
used for dilution, so long as the rate of dilution is kept in 
the proper proportion. After having once found the strength 
of the stock solution, any desired amount of this can be made 
to the proper dilution at any time. 
When an acetic acid solution is to be kept on hand for some 
time, it is desirable to add a small amount of pure mercuric 
chlorid (corrosive sublimate), for one liter about as much 
as will lie in a thin layer on a silver dime, in order to prevent 
change of strength by fermentation. The solution should be 
kept in tighty-stoppered bottles. 
For those who have had no experience in making standard 
solutions or who lack requisite facilities, it is recommended 
that normal solutions be obtained from some reliable chemical 
supply-house. The address of the most convenient dealers can 
be obtained from the agricultural college or experiment station. 
(3) Phenolphthalein solution. This is made by dissolving 
one gram of dry, powdered phenolphthalein in 100 cc. of 50 
per ct. alcohol. Some samples of phenolphthalein are quite 
acid and it is well to add to the prepared solution a few drops 
of dilute alkali until the solution acquires a slightly pinkish 
color. 
PERFORMING THE OPERATION. 
(1) Measuring and diluting sample of milk. The milk to be 
tested is well mixed and a 17.6 cc. pipette filled to the mark 
and the milk run into a 200 cc. flask. Then one adds about 
80 cc. of pure, soft water (preferably, distilled), filling the 
globe-shaped portion of the flask about half full. In pouring 
the water in, any milk adhering to the inside wall of the neck 
of the flask is washed down into the flask. 
(2) Neutralizing the milk. Add 1 ce. of phenolphthalein 
solution to the diluted: milk and then run into it the alkali 
solution from a burette, in small portions, shaking vigorously 
