IO8 MODERN METHODS OF TESTING MILK 



cator and (6) an ordinary white teacup. The alkali 

 solution must be of guaranteed accuracy and should 

 be obtained only from a reliable chemical or dairy- 

 supply house. 



The test is conducted as follows : Into the 1850 cc. 

 bottle one empties the small bottle, containing 37 cc. 

 of normal alkali solution, rinsing the small bottle with 

 water once or twice and adding the rinsings to the 

 large bottle, which is then filled to the mark with wa- 

 ter. Use only clean, soft or, preferably, distilled wa- 

 ter. This large bottle is kept tightly stoppered. Meas- 

 ure into a white teacup 17.6 cc. of the material to be 

 tested, rinse the pipette with clean water, adding the 

 rinse water to the sample in the cup, and then add 

 5 or 10 drops of indicator. From the graduated cyl- 

 inder, filled to the 100 cc. mark with the dilute alkali 

 solution, one pours the solution in portions into the 

 sample to be tested, agitating after each addition of 

 alkali, and continuing the addition of alkali solution 

 until the pink color does not disappear on agitation. 

 Then, from the cylinder read the number of cubic cen- 

 timeters of alkali used. Each cubic centimeter corre- 

 sponds to .01 per cent of acid. 



COMPARISON OF DIFFERENT FORMS OF 

 ACID TESTS 



Mann's acid test has the advantage of furnishing 

 the alkaline solution ready for use at any time. It 

 has this serious disadvantage, that the alkaline solu- 

 tion is in constant danger of becoming weakened by 

 absorption of carbon dioxide when exposed to the air. 

 A weakened alkali solution gives higher results of 



