28 MILK 
to c.c. N/,; acid per 1000 c.c. of milk will give 
the ‘‘aldehyd number.’’ Richmond finds that 
this multiplied by 0.17 gives in most cases a close 
approximation to the total proteins obtained by 
the Kjeldahl method. 
Calculation Method.—Olson has shown that in 
normal milks the proteins may be calculated with 
close approximation by the formula 
in which p is protein and ¢ total solids. 
DETERMINATION OF SPECIAL PROTEINS.— 
Casein and albumin may be determined by Sébe- 
lein’s method: 20 c.c. of the sample are mixed 
with 40 c.c. of a saturated solution of magnesium 
sulfate and powdered magnesium sulfate stirred 
in until no more will dissolve. The precipitate 
of casein and fat, including the trace of globulin, 
is allowed to settle, filtered, and washed several 
times with a saturated solution of magnesium 
sulfate. The filtrate and washings are saved for 
the determination of albumin. The filter and 
contents are transferred to a flask and the 
nitrogen determined by the method described 
above. The nitrogen so found, multiplied by 
6.38, gives the casein. 
The filtrate and washings from the determina- 
