MILK. 223 



0.3 g. of copper sulphate, and 10 g. of potassium sulphate, at 

 first gently and then more strongly, until the contents of 

 the flask have a light-blue or green color. Place 25 cc. of 

 fifth-normal acid in the receiver. For further details see the 

 " Determination of Nitrogen according to Kjeldahl " in the 

 chapter on ' ' Urine." 



If the amount of proteid be calculated by multiplying the 

 amount of nitrogen obtained by 6.25, as is customary, the 

 result will be somewhat too high. According to I. Munk, 

 it is better to use the factor 6.0 for cow's milk, and for hu- 

 man milk 5.77. See the " Determination of Total Proteid " 

 below. 



5. Separate Determination of Casein and Albumin (accord- 

 ing to Schlossmann 1 ). Dilute 10 cc. of milk with 3-5 parts 

 of water and cautiously warm to 40 over a free flame or, 

 better, in a water-bath, then add 1 cc. of concentrated solution 

 of potash-alum and stir thoroughly. If a flocculent precipi- 

 tate, which settles quickly, does not form, then continue to 

 add the alum solution, 0.5 cc. at a time, until the coagulation 

 and precipitation take place completely. Of course time 

 (half a minute) must be allowed before each addition rf 

 the alum solution for the settling of the precipitate; th^ 

 temperature is to be kept constant at 40. A slight excav, 

 of the alum solution makes no difference. After the com- 

 pletion of the precipitation let stand a few minutes and then 

 filter. When the filtrate is perfectly clear, which may requ : re 

 filtering two or three times through the same filter, wash the 

 precipitate a few times on the filter with water and determine 

 the nitrogen by the Kjeldahl method. From the amount 

 of nitrogen found calculate the amount of casein by multi- 

 plying by 6.37. 



Add to the filtrate 10 cc. of tannin solution, 2 filter off the 



1 Zeit. f. physiol. Chemie, 22, 213. 



8 The mixture recommended by Almen, consisting of 4 g. of tannin, 



