DETERMINATION OF FATS. 35 



readily removed than the ethyl ether. In any case the 

 gravimetric methods just described are by far the sim- 

 plest and most quickly carried out. 



C. SOXHLET'S AEROMETRIC METHOD. (Applicable 

 only to cow's milk.) 



The method depends upon the principle of estimating- 

 the specific gravity of the ether solution of the fats. A 

 measured quantity of milk is treated with potassium 

 hydrate solution and ether. By shaking, the fat is taken 

 up by the ether, and the specific gravity of the resulting 

 solution determined in a special apparatus. For this 

 process the following reagents and equipment are neces- 

 sary : 



1. Potassium hydrate solution, specific gravity 1.27 

 (400 grams of solid caustic potash are dissolved in water 

 and after cooling, the solution is made up to one liter). 



2. Ethyl ether, purified by shaking with one-tenth to 

 two-tenths volume of water, and pouring off the clear 

 liquid. 



3. Ether, commercial ethyl ether. (\'eed not be puri- 

 fied.) 



4. A vessel of about four liters capacity to be filled 

 with water at 17 to 18 degrees C. 



5. Three pipettes ; one 200 c. c, one 60 c. c, and one 

 10 c. c. capacity. 



6. Several milk flasks of one-half liter capacity. 



7. Two accurate areometers with thermometers : one 

 for skimmed milk, and one for whole milk. These spin- 

 dles are to be used in a specially constructed cylinder 

 which is kept surrounded with cold water. 



8. A rubber hand bellows. 



Details of the Method: The milk is 

 brought to a temperature of 18 degrees by holding the 

 bottle in water of the proper temperature. The sample 



