86 MILK 



or KOH with 90 c.c. of water formed a clear solution, the casein 

 dissolving completely. If a minute amount of a solution of a 

 barium, strontiom, or calcium salt was added to the clear casein 

 solution the characteristic opalescence of casein solutions devel- 

 oped. Elementary analysis gave the following result: Moisture 

 1.09 per cent.; in the dry substance, C. 53.50, H. 7.13, N. 15.80, 

 P. 0.71, S. 0.72, O. (by difference) 22.08, and ash 0.06 per cent." 

 Ash-free paracasein is prepared according to Van Slyke and 

 Bosworth according to the following method: " Separator-skimmed 

 milk is warmed up to 37 C. and rennet extract (Hansen's) added 

 in the proportion of 0.12 c.c. for each liter of milk. The mixture 

 is allowed to stand until the paracaseinate has separated as com- 

 pletely as possible. The resulting curd is stirred vigorously in 

 order to break it into small pieces and hasten the separation of 

 whey. After the curd has settled the whey is removed by siphon. 

 The paracaseinate is washed with distilled water several times, 

 and finally 5 liters of water are added for each liter of milk origin- 

 ally used. Dilute NH 4 OH (6 c.c. strong reagent diluted to 

 1000 c.c.) is then added and the mixture stirred until the para- 

 caseinate is dissolved. The process of reprecipitation, washing, 

 and dissolving is continued as in the preparation of casein. The 

 remaining calcium is finally separated by addition of ammonium 

 oxalate and centrifuging as described in the preparation of casein. 

 The remaining calcium is finally separated by addition of am- 

 monium oxalate and centrifuging as described in the preparation 

 of casein. One preparation of paracasein contained 0.07 per 

 cent. ash. One gram gave a clear solution when dissolved in 10 

 c.c. of N. 0.1, NH 4 OH, and 90 c.c. water. Another preparation 

 with a high ash content gave the following analysis: Moisture 

 1.63 per cent.; in the dry substance, ash 0.61, C. 53.50, H. 7.26, 

 N. 15.80, P. 0.83, S. 0.87, O. (by difference) 21.13 per cent. An- 

 other preparation with exceptionally low ash content gave: Ash 

 0.07, P. 0.71, and S. 0.72 per cent." 



PROPERTIES OF BOVINE CASEIN 



Casein is an acid, forming mono-, di-, and tricaseinates, and 

 replaces C02 in carbonates. In milk it is a complex calcium salt 

 containing phosphorus. Courant mixed casein, lime-water, and 

 phosphoric acid and obtained a substance which closely resembled 

 the casein of milk. It has not yet been determined whether casein 

 is a complex chemical combination or whether it is merely a mix- 

 ture of several compounds. However, we do know that all parts 

 of it are necessary for rennet coagulation. 



vPure casein is insoluble in water and alcohol, but dissolves 

 readily in acids unless they are highly diluted. It dissolves in 



