DETERMINATION OF FATS. 33 



too rapidly the vapor wifl not be entirely condensed, and 

 a considerable part of it will thus be lost. The quantity of 

 ether used must be sufficient to fill the tube (a) to the 

 top of the siphon tube (b) at least one and a half times. 

 The different parts of the apparatus should be connected 

 by tightly fitting corks or by ground glass joints. 



The flask containing the fat in ether solution is placed 

 on the water bath and the ether distilled off. It is then 

 placed in drying oven and dried at 105 degrees C. to con- 

 stant weight. The weight of the empty flask having been 

 previously ascertained, the increase in weight will indi- 

 cate the weight of fat in the sample. From this data the 

 per cent of fats may be readily calculated. 



Instead of evaporating with sand on the water bath — 

 a process which takes more or less time — Fernandez- 

 Krug and Hampe recommend the mixing of five or ten 

 c.c. of milk witli 7.5 to 15 grams of powdered kaolin and 

 5 to 10 grams of water-fee sodium sulphate. In this way 

 a perfectly dry mass is obtained which may be extracted 

 at once with ether. 



Pfeiffer suggests precipitating out the albuminoids and 

 fat of the milk and filtering through a folded filter. The 

 residue is washed a few times with water, dried at 100 

 degrees and placed with the filter in a Soxhlet extraction 

 apparatus. To precipitate the fats and albuminoids 

 trichloracetic acid or copper hydrate may be used. 



B. THE EXTRACTION OF FATS BY MEANS OF PE- 

 TROLEUM ETHER. (The Lieberman-Weiss Method.) 



Liebermann and Szekely and Weiss propose petro- 

 leum ether as a solvent in determining the per cent of 

 fat. The method is applicable to cows' and human milk 

 and may be carried out rapidly without the use of a 

 great deal of apparatus. A glass cylinder about 15 cm. 



