AMERICAN ASSOCIATION TEST 105 



form and correspond closely to chemical analysis (The Rose- 

 Gottlieb test), as the accompanying table shows. 



(2) There is much less trouble with a deposit in the test 

 bottles than is the case where the other alcohols are used. 



(3) Normal butyl (w-butyl) alcohol, being a single alcohol 

 that is readily purified, is free of impurities while the amyl and 

 iso-butyl alcohols are not likely to be. In blank tests made, 

 that is, when water was substituted for buttermilk in a test, a 

 short column of some impurity rose into the neck of the test 

 bottle when the amyl and iso-butyl alcohols were used, but not 

 when w-butyl alcohol was used. 



(4) The n-buty] alcohol is quite stable and is not at all likely 

 to be attacked by the sulphuric acid, while the other alcohols 

 mentioned are iso-alcohols that run off into chains and are less 

 stable and are likely to be mixtures. 



(5) The w-butyl alcohol does not possess either a pungent or 

 an otherwise offensive flavor or odor, and consequently is much 

 pleasanter to use than the others. 



(6) The w-butyl alcohol is the lowest in price of the dif- 

 ferent alcohols, and, being stable and free of impurities, is the 

 most reliable alcohol to use. Even the cheaper grade of this 

 alcohol (the " practical ") contains no impurity excepting pos- 

 sibly a slight amount of moisture. 



Extensive and carefully conducted investigations have 

 shown that the right amounts of commercial sulphuric acid 

 and w-butyl alcohol to use in testing a 9-gram sample of 

 skim-milk or butter-milk are as given in the directions which 

 follow : 



Directions for making a test: 



Chemicals. Commercial sulphuric acid. 

 Normal butyl alcohol. 



i. Place the chemicals and buttermilk in the test bottle in 

 the following amounts and the order indicated. 



(a) 2 c.c. of w-butyl alcohol. 



(b) 9 c.c. of buttermilk. 



(c) 7 to 9 c.c. of commercial sulphuric acid. 



Vary amount of acid to suit its strength. The right amount 



