25 



the fat globules settles quickly, leaving the fluid perfectly clear. 

 The fluid is decanted through a filter which had previously been 

 dried at' 110° C, and weighed between two watch-glasses. The 

 precipitate is then stirred up with 100 c.c. of water. After al- 

 lowing to settle, the water is likewise decanted through the filter, 

 and finally the precipitate is brought upon it. The beaker is then 

 cleaned by means of a nibber washer, and washed with water xintil 

 everything is transferred to the filter. Thus, about 240 c.c. of 

 filtrate are obtained, which are diluted to make it exactly 250 c.c 

 This filtrate is used for the determination of milk sugar. 



The beaker contains always some fat, which must be added to 

 the fat obtained from the albumen precipitate, and is, therefore, 

 set aside until this operation is in order. The copper casein pre- 

 cipitate, containing all the albuminates and the fat of the milk, ex- 

 cepting that portion which was left on the beaker, is then, by 

 means of a small spatule, well distributed over the whole surface 

 of the filter, which had been previously transferred to a large watch- 

 glass. This aids the evaporation of the water considerably, and 

 becomes necessary from the fact that the application of higher 

 temperatures must be avoided. To effect drying, the filter may 

 be exposed to the sun, or the watch-glass may be placed where it is 

 exposed to a moderate temperature. From time to time the pre- 

 cipitate is again worked with the spatule, care being taken that 

 the filter is not injured. After some time the residue becomes a 

 finely divided dry powder, which can easily be collected in the 

 point of the filter, and from which the fat can be extracted. 



Determination of fat : The ordinary open extraction of the 

 fat, consisting in the washing of the precipitate with warm ether 

 on an open funnel, until the precipitate is exhausted, has disadvan- 

 tages, resulting not only in a loss of fat by effervescence, but also 

 in the waste of a considerable quantity of ether. Far more eco- 

 nomical is the use of a closed apparatus for the extraction of fat. 



