27 



sand bath, which is cautiously heated by means of a Bunsen 

 burner. The heat must be so regulated that the filter swims con- 

 tinually to one-half its height in condensed ether, and the cooling 

 must be sufficient to prevent the escape of ether. Thus the com- 

 plete extraction of the fat may be effected in about one hour. The 

 funnel is then removed, and the flask is connected with a cooler, 

 and the ether, which contains alcohol, recovered by distillation at 

 very low temperature. The flask is then put in an air bath, laying 

 it on its side, and dried for one or two hours at a temperature of 

 lOQ to 105° C. After cooling in a desiccator, it is weighed. 



The increase of weight corresponds to the amount of fat con- 

 tained in the quantity of milk taken for analysis. The residue in 

 the filter is then driedfor two hours at from 110 to 120° 0., and 

 weighed between two watch-glasses. After this it is transferred 

 to a porcelain or platinum crucible, and incinerated. 



Weight of filter + dry coagulum, 

 Minus weight of filter + ashes. 



Leaves albuminous substance. 



The nitrogen determination in this substance, if required, must 

 be made by Dumas' method, on account of the presence of cupric 

 oxide, which, in an attempt to use Will Varrentrape's method, 

 would cause a loss by the partial destruction of the ammonia. The 

 determination of albuminates by simple incineration, is, however, 

 sufficiently exact. 



For a description of Dumas' method for the determination of 

 nitrogen, we refer to Fresenius, Quantitative Analysis. 



A separation of so-called albumen and casein is wrong ; a de. 

 termination of the sum of all albuminous substances is, generally^ 

 all that is required, if the investigation is not to go into such de- 

 tails as those mentioned on pages 6 and 7. 



Determination of Milk Sugar. 



The sugar of milk is determined in the 250 c.c. fluid which 

 have been filtered from the coagulum obtained by the addition of 

 cupric sulphate to milk. The method adopted by the author con- 

 sists in the titration by means of Fehling's solution. 



