74 MIIK PRODUCTS 



In the examination of cream a third extraction 

 is necessary, but with evaporated and condensed 

 milk the third extraction does not recover more 

 than o. 02 or 0.03 % of fat, and may be omitted. 



Evaporate the liquid slowly on a steam bath 

 and dry the fat in steam oven until its weight is 

 constant . Weigh after one hour and then at half- 

 hour intervals. As soon as the fat begins to gain 

 in weight stop drying and take the next previous 

 weight. Increase of weight is due to oxidation 

 after all moisture and alcohol are gone. In all 

 cases the drying should be completed the day it 

 is begun. 



Double Extraction. — The following is given as a 

 provisional A. O. A. C. method: Extract with 

 ether, as usual, about 5 grams of a 40 % solution, 

 dry, leave the tubes in a dish containing at least 

 500 c.c. of water, dry, extract again with ether for 

 four hours. 



Sugars. — If regard is to be given to the 

 presence of invert-sugar, a special method must 

 be followed. The processes first given consider 

 lactose and sucrose only. The heating employed 

 in the manufacture of condensed milk may 

 reduce the rotatory power of lactose suflEiciently 

 to cause error in the polarimetric method. The 

 reducing power with alkaline copper solutions 

 is not seriously affected. 



Determination of sucrose may be made by 



