CHAPTER XXVII. 



CASEIN. 



The separation of casein from milk for cheese-making 

 purposes has been practiced for over two thousand years, 

 but only during the last few decades has scientific research 

 revealed the multitude of uses to which this product may 

 be put in the technical industries. Casein to-day is manu- 

 factured on a large scale and used in the preparation of 

 paint, glue, paper, dress goods, as imitation ivory, horn, 

 etc., and as a concentrated foodstuff. 



Casein exists in milk not in true solution, but in sus- 

 pension. It may be separated out by the following means : 

 (i) filtration through a porous clay filter, (2) centrifugaliz- 

 ing, (3) precipitation by dilute acids, (4) precipitation by 

 ferments, and (5) precipitation by salts. Casein, when 

 dried, forms a horny mass insoluble in water or dilute acids, 

 but soluble in alkalis and concentrated acids. 



Statistics show that the use of dry casein has increased 

 100 per cent during the last five years, and that Germany 

 consvraies about four thousand tons annually. The entire 

 consimiption in Europe and America is placed at about 

 fifteen thousand tons. The United States Census of 1909 

 places the casein production in this country at almost 

 seven thousand tons, an increase of 12 per cent in five 

 years. 



Preparation of Casein. — In the chemical laboratory, 

 casein is prepared by diluting the milk to about five times 

 its volxmie, and adding sufficient acetic acid to make the 



