66 Testing Milk and Its Products. 



each addition, so as not to cause it to break on account 

 of the heat evolved in mixing the acid and the water. 

 Never dilute sulfuric acid by pouring water into it. 



A helpful suggestion for using acid that is too strong 

 or would give a charred fat on account of high tem- 

 perature of acid or milk, or both, has been made by M. 

 L. Holm, Assistant Chemist Chicago Dept. of Health, 

 viz., to add 2 cc. of 80 per cent, glycerin (80 parts of 

 commercial glycerin and 20 parts of water, by volume) 

 to the milk sample, prior to adding the acid. 1 The gly- 

 cerin protects the milk to some extent from the acid be- 

 fore the two are mixed, and a clear fat may thus often 

 be secured under otherwise unfavorable conditions. The 

 results appear not to be influenced by the addition of 

 the glycerin. 



75. If the acid is a little too weak, correct results 

 may be obtained by using more than the specified quan- 

 tity, say 20 cc. If a good test is not obtained with this 

 quantity of acid, a new lot must be secured, as its spe- 

 cific gravity in such a case is below 1.82. The observing 

 operator will soon be able to judge of the strength of 

 the acid by its action on milk in mixing the two liquids 

 in the Babcock test bottles ; it is indeed remarkable 

 what slight differences in the specific gravity of the 

 acid will make themselves apparent in working the test, 

 as regards the rapidity with which both the curdled 

 milk is dissolved and the mixture of acid and milk turns 

 black. 



1 American Food Journal, 1907, No. 7, p. 28; Hoard's Dairyman, Nov. 

 8, 1907. 



