FOODS AND FOOD ADULTERANTS. 







44 



-45 



burette into the flask (previously carefully cleaned and dried), until 

 the meniscus at the ground edge of the neck passes from the concave 

 to the convex form, a change which is effected by a single drop. When 



the flask is nearly full at least five minutes 

 should be allowed for the water to settle 

 in the burette. The cubical contents of 

 the flask are now noted from the burette. 

 Reagents. A solution of caustic potash 

 having a specific gravity of 1.27. A solu- 

 tion of aqueous ether the same as is used 

 in Soxhlet's method. 



Manipulation. Fifty cubic centimeters 

 of the milk in the cylinder described above 

 are treated with 5cc. of the potash solu- 

 tion, well shaken and allowed to stand for 

 five minutes. This is next treated with 



45 ^ 50cc. of the aqueous ether, and gently 



shaken for ten seconds. The cylinder is 

 now allowed to stand for twenty minutes, 

 receiving every half minute one or two 



.45 light vertical blows. At the end of this 



timo the separation of the clear ether layer 

 is usually complete, yet it sometimes hap. 

 pens that some of the emulsion adheres to 



.47 the under part of the flask in the form of 



a transparent covering. By means of a 

 gentle rotating movement imparted to the 

 cylinder this emulsion is collected and rap- 

 idly settles. 



With a 20cc. pipette the clear ether solution is removed. Before this 

 is allowed to flow into the flask that part of it which has been dipped 

 into the solution is carefully wiped, so that no part of the potash liquid 

 c!in drop into the flask. The ether solution is now evaporated, and the 

 residue dried for at least half an hour at a tern perature of 110 O., or what 

 is still better, over a small flame until the odor of the decomposed butter 

 is detected. The whole is now cooled in a dessiccator. It can now 

 be weighed, if the weight of the flask is known, or it can be estimated 

 volume trically. 



In case the estimation is made volumetrically, it must be carefully 

 observed that the solidified fat contains no air bubbles. In case any 

 air bubbles are noticed the fat must be again melted and warmed until 

 they have all disappeared. 



Into the flask containing the solidified butter fat water is again run 

 out of the burette under the same conditions which obtained in deter- 

 mining the contents of the flask at first. It is of the greatest irnpor- 



Fifi. 3. 



FIG. 4. 



