224 QUANTITATIVE ANALYSIS. 



voluminous precipitate which forms, and, after washing 

 three times with fresh water, determine the amount of nitro- 

 gen by the Kjeldahl method. From the amount of nitrogen 

 found calculate the amount of albumin and globulin by 

 multiplying by 6.37. 



6. Determination of the Total Proteid according to Ritt- 

 hausen and I. Munk. 1 Place 10 cc. of human or cow's milk 

 in a 250-cc. beaker, dilute with water to 100 cc. (with human 

 milk dilution to 60 cc. is sufficient), heat, and add 1 to 2 cc. 

 of alum solution, then when the fluid just begins to boil 2 to 5 

 cc. of a paste of cupric hydroxide, and continue the boiling for 

 some minutes. The finely flocculent precipitate, which set- 

 tles quickly, as soon as the mixture has been coagulated by 

 heating, is filtered while still warm, washed on the filter with 

 hot water, and the whole filter treated while still moist accord- 

 ing to Kjeldahl. 



The cupric hydroxide is prepared according to Stutzer 

 as follows: 100 g. of crystallized copper sulphate are dis- 

 solved in 5 liters of water and 2.5 g. of glycerine are added. 

 Dilute sodium hydroxide solution is then added until the fluid 

 reacts alkaline, the cupric hydroxide is then filtered off and 

 ground with water containing 5 g. of glycerine to the liter. 

 By repeated decanting and filtering the last traces of alkali 

 are removed. The product remaining on the filter is then 

 ground and diluted with water which contains 10 per cent, 

 of glycerin, so that it forms a homogeneous mass which may 

 be measured out with a pipette. This is kept in the dark in a 

 well-closed bottle. The amount of copper oxide in the pasty 

 mass may be determined by evaporating a measured volume 



8 cc. of 25 per cent, acetic acid, and 190 cc. of 40 to 50 per cent, alcohol, 

 gives the best results. 



1 See Ritthausen, Jour. f. prakt. Chemie N. F. 15, 329; Emil Pfeiffer, 

 Analyse der Milch. Wiesbaden, 1887. I. Munk, Virchow's Arch. 134, 

 501 (1893). 



