Testing the Purity of Milk. 133 



149. Size of measure necessary. It is not necessary 

 to use a No. 10 shell for a measure in working the pre- 

 ceding method; one of any convenient size that can be 

 filled accurately and quickly, will answer the purpose 

 equally well, if a measure of the same size is used for 

 both the sample and the tablet solution. Each measure- 

 ful of tablet solution made up as directed, will in this 

 case represent one-tenth per cent, of acid in the sam- 

 ple tested. 1 



150. b, Cream. Cream can be tested in the way al- 

 ready described for testing the acidity of fresh milk, by 

 adding to one measureful of cream in the cup as many 

 measures of tablet solution as are necessary to change 

 the color of the cream when the two liquids are thor- 

 oughly mixed. If one measure of tablet solution colors 

 one measure of cream, this contains less than .1 per 

 cent, acid; if five measures of tablet solution are re- 

 quired, the cream contains about .5 per cent, acid, etc. 

 By proceeding in the manner described, the operator 

 can estimate the acidity to within .05 per cent, of acid, 

 if half measures of tablet solution are added. The re- 

 sults thus obtained are sufficiently delicate for all prac- 

 tical purposes. 



151. Detection of boracic-acid preservatives in milk. The 



application of the alkaline tablet test for detecting boracic acid in 

 milk was first discussed in bulletin No. 52 of Wisconsin experi- 

 ment station. The acidity of the milk is increased by the addi- 

 tion of boracic acid, but neither the odor nor the taste of the 

 milk is affected thereby. By adding to sweet milk the amount 



1 In European creameries and city milk depots the alcohol test is 

 often applied to every can of milk received; milk that is sufficiently 

 sour to be noticed by the taste, will coagulate when mixed with an 

 equal volume of 70% alcohol. 



