1 8 MILK 



materials may be removed from the tube, and, 

 replacing the parts of the apparatus, much of 

 the solvent may be redistilled into the extractor, 

 thus recovering the liquid. Care must be taken 

 not to distil the contents of the flask closely or 

 heat strongly, lest some of the more volatile of 

 the dissolved matters pass into the distillate. 



Roese-GottUeb Method. — This is now being used 

 for milk-products as well as for milk. For de- 

 tailed description, see page 72. 



Centrifugal Methods. — Although almost all the 

 fat of milk may be separated by the centrifuge, 

 the emulsion is not destroyed and the volume of 

 cream is merely suggestive as to the fat-content 

 of the milk. To obtain a clear fatty layer in 

 condition for close measurement it is necessary 

 to use chemicals. The methods at present most 

 employed depend essentially on one devised by 

 Gustaf DeLaval, who took out a patent in Sweden 

 for the use of a mixture of twenty volumes of 

 strong acetic acid and one volume of strong 

 sulfuric acid. This mixture coagulates and then 

 dissolves the proteins, destroys the emulsion, but 

 does not otherwise aflfect the fat and does not 

 act on the lactose. By brief whirling in a cen- 

 trifuge the fat collects in a clear sharply defined 

 layer. DeLaval took out patents in several 

 countries subsequent to the above date. 



Leffmann and Beam devised a method in which 



