Testing the Acidity of Milk and Cream. 131 



fore, rich cream need not be ripened to as high a degree 

 of acidity as thin cream. A table is given in the Iowa 

 bulletin referred to, showing the relation between the 

 richness and the acidity of cream. 



145. Spillman's cylinder. The graduated cylinder shown in 

 fig. 43 was devised by Professor Spillman for use in testing the 

 acidity of milk and cream with Farrington's alkaline tablets. 

 The following directions, are given for making 

 tests with this piece of apparatus: 1 



' ' All that is needed in addition to the acid-test 

 graduate shown in the accompanying illustration, 

 is a common prescription bottle of six or eight 

 ounce capacity, and a package of Farrington's 

 alkaline tablets. Fill the bottle with water and 

 add one tablet for each ounce of water in the 

 bottle. Shake the bottle frequently to aid in dis 

 solving the tablets. 



' ' Making the test. In making the test, the 

 acid-test graduate is filled to the zero mark with 

 the milk or cream to be tested. The tablet solu- 

 tion is then added, a little at a time, and the 

 graduate shaken after each addition, in order to 

 thoroughly mix the milk and the tablet solution. * 

 In shaking the graduate, give it a rotary motion p IG 

 to prevent spilling any of the liquid. Continue man's cylinder, 

 adding the tablet solution until a permanent pink fining he acid- 

 color can be detected in the milk. The level of Ky of cream or 

 the liquid in the graduate, measured by the scale 

 on the graduate, will then show the per cent, of the acidity of the 

 milk. It is best to stand the graduate on a piece of white paper, 

 so that the first pink coloration of the milk may be easily de- 

 tected. ' ' 



146. The Marschall acid test (see fig. 44) is a con- 

 venient apparatus for determining the acidity of milk, 

 cream, or whey. 2 It is used with a tenth-normal alkaline 



1 Washington experiment station, bulletin 24. 

 * See Wis. exp. sta.. bull. 129. 



