136 Testing Milk and Its Products. 



suits 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 the 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 

 of boracic acid which will keep it sweet 36 hours, its acidity may 

 be increased to .35 per cent., in a sample of milk which pre- 

 viously tested perhaps only .15 per cent. acid. 



As before stated, unadulterated milk will usually smell or 

 taste sour or "turned," when it contains .30 to .35 per cent, acid 

 (121) ; milk testing as high as this limit, which neither smells 

 nor tastes sour in any way, is therefore in all probability adul- 

 terated with some preparation containing boracic acid or a simi- 

 lar compound. 



152. "Alkaline tabs." These are not the alkaline tablets, 

 but a substitute which was put on the market by a New York 

 firm. The outfit furnished consisted of four packages of paper 

 discs made of heavy filter paper, each of about the size of an old- 

 style copper cejit; two packages of square paper; one glass of about 

 10 cc. capacity, and one small glass bottle. An investigation of 

 these "Tabs" soon disclosed the fact that they were entirely 

 inaccurate, and that no dependence could therefore be placed on 

 the results obtained by their use. 



Questions. 



1. If 20 cc. cream require 12 cc. ^ alkali for neutralization, 

 what per cent, acid in the sample T 



2. If 1 cc. jj alkali neutralize .009 gram lactic acid, what is 

 the per cent, of acid in a sample of cream, which required 12 cc. 

 alkali for 25 cc. of cream! 



3. What apparatus and strength of solution must be taken 

 to show per cent, acidity directly from cc. alkali used with Far 

 rington's alkaline tablets! 



4. If cream testing 20% fat has an acidity of .6%, what will 

 be the corresponding acidity of cream testing 40% fat! 



