TOTAL PROTEIDS. 33 



Usually not more than 150 c. c. need be collected. 

 The acid remaining unneutralized is determined by ti- 

 tration with the standard barium hydroxid, using phe- 

 nolphthalein as an indicator, and the nitrogen distilled 

 over as ammonia, calculated. The nitrogen figure 

 multiplied by 6.38 will give that of the total proteids. 



CASEIN AND ALBUMIN. 



20 c. c. of the milk are mixed with 40 c. c. of a sat- 

 urated solution of magnesium sulfate and powdered 

 magnesium sulfate stirred in until no more will dissolve. 

 After settling, the precipitate of casein and fat, includ- 

 ing the trace of globulin, is filtered and washed several 

 times with a saturated solution of magnesium sulfate. 

 The filtrate and washings are saved for the determina- 

 tion of albumin. The filter and contents are trans- 

 ferred to a flask and the nitrogen determined by the 

 method described above. The nitrogen so found mul- 

 tiplied by 6.38 gives the casein. 



The filtrate and washings from the determination of 

 casein are mixed, the albumin precipitated by a solution 

 of tannin, filtered and the nitrogen in the precipitate de- 

 termined as above. The same factor is used. 



On account of the difficulty of washing the pre- 

 cipitated casein, we prefer to proceed as follows : 

 20 c. c. of the milk are mixed with saturated mag- 

 nesium sulfate solution and the powdered salt added 

 to saturation. The mixture is washed into a graduated 

 measure with a small amount of the saturated solution, 



