204 THE ANALYSIS OF MILK PRODUCTS. 



by 0-00735, and subtract the resulting figure from the specific 

 gravity ; the percentage of added water, if present, is calculated 

 from the fat, and the corrected specific gravity in the same way 

 as the extent of watering of milk is deduced (p. 361). 



Human Milk. As the quantity of the sample is often 

 very limited; the Gerber-Ritthausen method for the analysis 

 of human milk is useful ; 5 c.c. are diluted with 100 c.c. of 

 water, 3 c.c. of copper sulphate solution added, and caustic 

 soda solution drop by drop till the precipitate settles readily ; 

 the precipitate is collected in a Gooch crucible, washed with 

 water, and dried in the water-oven. The fat is extracted by 

 percolating with ether, the crucible after several percolations 

 being allowed to stand in a beaker containing ether overnight. 

 The ether is evaporated and the fat weighed, and if very dark 

 green in colour, the fat should be extracted with dilute hydro- 

 chloric acid, and the amount of copper estimated and subtracted 

 from the weight. The refractive index of the fat may be deter- 

 mined. The Gooch crucible is dried to constant weight, and 

 ignited ; the difference between the two weights gives the pro- 

 teins. The milk-sugar may be estimated in the filtrate by 

 Fehling's method. 



The author has found that the aldehyde figure multiplied by 

 0-134: gives a close approximation to the proteins. 



