28 MILK 



to c.c. ^/i acid per looo 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 



t 



p = t 



1-34 



in which p is protein and t total solids. 



Determination of special proteins. — 

 Casein and albumin may be determined by S6be- 

 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 imtil no more wUl 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 foimd, multiplied by 

 6.38, gives the casein. 



The filtrate and washings from the determina- 



