36 METHODS OF QUANTITATIVE ANALYSIS. 



is well shaken and 200 c. c. of it transferred to a milk 

 flask. It is then treated with 10 c. c. of the potassium 

 hydrate solution and mixed by shaking. To- this 60 

 c. c. of ether, previously saturated with water, are added 

 and the flask then quickly stoppered. The flask is al- 

 lowed to stand in^ water bath at 18 degrees for 15 min- 

 nutes, and during this time it is shaken every half minute 

 (three or four vertical tosses each time). In this amount 

 of time the ether solution of the fats usually separates out 

 clear, but in case of milk very rich in fat a longer time is 

 required. 



The method of procedure may be best explained by 

 reference to the illustration (Fig. 3). 



The glass cooler (A) is filled with water at 18 degrees 

 C. The milk flask (B) which contains the ether-fat solu- 

 tion is provided with a two-hole stopper. Into one of 

 the holes is fitted the bent glass tube (C), allowing it to 

 protrude just through the cork. The other end of the 

 tube is connected with the hand bellows (D). Through 

 the other hole of the cork is put a longer glass tube 

 (E) also bent to a right angle. The tube should extend 

 m the bottle almost to the bottom of the layer of ether 

 solution. The end of the tube outside is connected 

 with the stem of the areometer cylinder (F) by a rubber 

 tube. The pinchcock (H) serves to hold the ether solu- 

 tion in (F). 



The Operation: By removing the stopper (L) 

 from the cylinder and opening the stopcock (H), the 

 fat solution is forced into the cylinder (F) by pressure 

 from the hand bellows. The cylinder is filled until the 

 areometer (G) floats freely, when the stopcock is quickly 

 closed. By adjusting the screw in the foot of the sup- 

 port the apparatus is brought to a vertical position. The 

 areometer and thermometer readings are then taken and 

 by referring these to the table following, the per cent of 



