FAT DETERMINATIONS 369 
bottle. The bottle should be whirled again for about a minute and then 
the percentage of fat read by means of a pair of calipers. This test is 
adapted to ice cream and cream with the exception that a larger bottle is 
used. 
Leffmann-Beam Test. The distinctive feature is the use of fusel 
oil, the effect of which is to produce a greater difference in surface ten- 
sion between the fat and the liquid in which it is suspended, and thus 
promote its readier separation. This effect has been found to be 
heightened by the presence of a small amount of hydrochloric acid. 
The test bottles have a capacity of about 30 ¢c.c. and are provided 
with a graduated neck, each division of which represents 9.1 per cent by 
weight of butter fat. 
Fifteen centimeters of the milk are measured into the bottle, 3 c.c. of a 
mixture of equal parts of amyl alcohol and strong hydrochloric acid 
added and mixed. Then 9 c.c. of concentrated sulphuric acid is added 
in portions of about 1 c.c.; after each addition the liquids are mixed by 
giving the bottle a gyratory motion. If the fluid has not lost all of its 
milky color by this treatment, a little more concentrated acid must be 
added. The neck of the bottle is now inimediately filled at about the 
zero point with one part sulphuric acid and two parts water, well mixed 
just before using. Both the liquid in the bottle and the diluted acid 
must be hot. The bottle is then placed at once in the centrifugal ma- 
chine; after rotation from one to two minutes, the fat will collect in 
the neck of the bottle and the percentage may be read off. 
Gerber’s Test. This test is applied as follows: The test bottles are 
put into the stand with the mouths uppermost; then, with the pipette 
designed for the purpose, or with an automatic measurer, 10 c.e. of 
‘sulphuric acid are filled into the test bottle, care being taken not to 
allow any to come in contact with the neck. The few drops remaining 
in the tip of the pipette should not be blown out. Then 11 c.c. of milk 
are measured with the proper pipette and allowed to flow slowly onto 
the acid, so that the two liquids mix as little as possible. Finally, the 
amyl alcohol is added. (It is important to use the reagents in the 
proper order, which is—sulphuric acid, milk, amyl alcohol. If the sul- 
phuric acid is followed by amyl alcohol and the milk last, then the result 
is sometimes incorrect.) A rubber stopper, which must not be dam- 
aged, is then fitted into the mouth of the test bottle, and the contents 
are well shaken, the thumb being kept on the stopper to prevent it 
coming out. As a considerable amount of heat is generated by the 
action of the sulphuric acid on the milk, the test bottle should be wrapped 
in a cloth. 
