34 CASEIN. 



this does not ensue below 120 to 130 C. Halliburton 

 noticed a change when casein suspended in water was heated 

 to 75 C. What happens to the casein when milk is boiled 

 still remains unknown. 



According to Richter, casein is precipitated from its solu- 

 tions by sodium chloride or magnesium sulphate without 

 change. Mineral acids in excess precipitate casein solutions. 

 The solutions of the alkali and calcium salts of casein do not 

 coagulate on heating. A lime-free solution of casein is not 

 coagulable by rennet, though it becomes so when a calcium 

 salt is added, even though in the meantime the rennet has 

 been rendered inactive by boiling. 



After Hammarsten had investigated this action of cal- 

 cium salts on the curdling of milk by rennet, S. Loevenhart 

 demonstrated that a similar effect is produced by the salts 

 of lithium, beryllium, magnesium, strontium and barium, as 

 also by the proto-salts of iron, cobalt, nickel and manganese. 



Purified casein is a snow-white, perfectly ashless powder. 

 The heat of combustion of 1 gramme of casein is 5 '858 cal. 

 It strongly reddens blue litmus paper, but is only soluble 

 to the extent of a trace in water, though soluble in alkalies 

 and in water containing calcium carbonate. It also dis- 

 solves in a 1 per cent, solution of sodium fluoride, and in 

 ammonium oxalate or potassium oxalate. From solution it 

 is precipitated by acids and by rennet. In the presence of 

 salts (sodium chloride, and especially sodium acetate) the 

 precipitation by acids is incomplete. When purified milk 

 casein is boiled for five hours with 3 parts of hydrochloric 

 acid (specific gravity 119), tyrosin, leucin, leucinide, C 5 H 7 NO, 

 a little aspargic acid and glutamic acid are formed. 



In the treatment of casein for the preparation of water- 

 proof coverings (paints, varnishes, etc.), and particularly of 

 plastic masses intended as substitutes for celluloid, or for 

 other purposes, an important part is played by substances 



