44 MODERN METHODS OF TESTING MILK 



dilution depends upon the strength of the acid used. 

 One should start with a small dilution and increase 

 gradually until the specific gravity of the acid becomes 

 1.82 to 1.83. After diluting the acid with water, the 

 mixture becomes hot, and it is necessary to allow it 

 to cool to 60 F. before testing with the acidometer. 



Useful indications regarding strength of acid. 

 After one has acquired some skill in making the Bab- 

 cock test, one can readily tell whether the acid is too 

 strong or too weak from its action when mixed with 

 milk in the test-bottle. One bases his judgment on 

 the rapidity with which the milk-casein is coagulated 

 and redissolved, and also upon the quickness with 

 which, and the degree to which, the mixture of acid 

 and milk turns dark. 



Keeping acid from air. The acid should be kept 

 in tightly stoppered bottles, because, if exposed to air, 

 it absorbs moisture and becomes too weak. The stop- 

 per should be glass, since a common cork stopper is 

 soon destroyed by the acid, and even rubber is not 

 long satisfactory. 



Care in handling sulphuric acid. Strong sulphuric 

 acid is extremely corrosive and is dangerous to han- 

 dle except with care. In contact with articles like 

 clothing or leather, it quickly ruins them, while on 

 the skin it causes serious burns in a short time. If 

 sulphuric acid gets upon one's skin, it should be imme- 

 diately and thoroughly washed with an abundance of 

 water, and this may be followed by washing with di- 

 lute ammonia or sodium carbonate. In case acid gets 

 on the clothing, treat it first with abundance of water 

 and then with ammonia. Red discoloration on cloth- 



