BUTTER. 305 



the tablet solution are made by filling a four-ounce bottle with 

 water and adding to it four tablets. The No. lo shell is filled 

 with the milk or cream to be tested. This measured quantity 

 is poured into a white cup. The same measure is then filled with 

 the tablet solution and this is poured into the cup. The two 

 liquids are thoroughly mixed, and the color of the mixture is 

 noted. If there is no change of color, another measure of tablet 

 solution is added. This is continued until the sample which 

 is being tested retains a pink color. As soon as the pink color 

 is obtained no more tablet solution is added. The per cent of 

 acid in the sample tested is found from the number of measures 

 of tablet solution it is necessary to add to one measure of the 

 milk or cream sample in order to produce the pink color. Each 

 measure of tablet solution represents one-tenth of one per cent 

 acid when tests are made in this way. 



The Most Delicate Method. — A more exact testing of acidity 

 can be made by using a 17.6-cc. pipette for measuring the milk 

 or cream to be tested and a loo-cc. graduated cylinder for measur- 

 ing the tablet solution. 



Five tablets are dissolved in 97 cc. of water in the cylinder, 

 and this solution is gradually poured into the 17.6 cc. of milk or 

 cream in a white cup. When sufficient tablet solution has been 

 added to produce the pink color in the sample tested, the operator 

 observes on the scale of the graduated cylinder the number of 

 cc. tablet solution used. Each cc. of this tablet solution is equal 

 to 0.0090 gr. lactic acid, and when 17.6 cc. of a sample is tested, 

 each cc. of the tablet solution is equal to .01 per cent acid in the 

 sample. The per cent of acid in each sample is therefore indi- 

 cated by the amount of tablet solution used in each case. 



Milk docs not smell or taste sour until. it contains about three- 

 tenths of one per cent acid. It has been found, however, that 

 milk containing over two-tenths per cent acid cannot be safely 

 pasteurized, because such milk sours very soon. These tablets 

 supply a quick means of sorting different lots of sweet milk, by 

 showing which contain less and which more than two-tenths of 

 one per cent acid. 



Cream is often ripened so far that the quality of the butter 

 is injured. The usual method of the butter-maker for testing 



