The Babcock Test. 65 



same volume of water as that of the acid weighed. The 

 specific gravity of the acid is obtained by dividing the 

 weight of the acid by the weight of the water. If the 

 quotient comes between 1.82 and 1.83 the acid is of 

 correct strength. The outside of the test bottle should 

 always be wiped dry before the liquids are weighed. 

 Unless great care is taken in measuring the acid and the 

 water, and in weighing both these and the test bottle, 

 the results obtained will not be trustworthy. 



74. Acid that is a little too strong can be used by 

 taking less than the required amount for each test, e. g., 

 about 15 cc. Operators are warned against reducing 

 the strength of the acid by adding water to it, as acci- 

 dents may easily occur when this is done. A too strong 

 acid can, if desired, be weakened by simply leaving the 

 bottle uncorked for a time, or by pouring the acid into 

 a bottle containing a small quantity of water. In the 

 'atter case the first portions of acid should be added 

 carefully, a little at a time, shaking the bottle after 

 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.^ The gly- 



' .\merlcan Food Journal, 1907, No. 7, p. LIS ; Hoard's Dairyman, Not. 

 1007. 



