and Casein. Peptone. 77 



the hydrochloric acid compound of which is insoluble in water and 

 dilute acid. The dyspeptone itself is quite readily soluble in cold 

 water, the solution remaining unchanged on boiling. 



Following are some of the reactions of dyspeptone. 



Addition of acetic acid to an aqueous solution of the substance 

 produces a heavy white precipitate insoluble in moderate excess, but 

 partially soluble in a large excess of the acid. On heating the strongly 

 acid fluid, the precipitate dissolves completely and the fluid remains 

 clear on cooling. Addition of potassium ferrocyanide to the clear 

 acid fluid gives only a slight turbidity. 



Dilute hydrochloric and sulphuric acid both give a heavy white 

 precipitate, insoluble in slight excess of acid, but entirely soluble 

 in a large excess on application of heat. Even 0-2 per cent, hydro- 

 chloric acid precipitates the dyspeptone completely. 



Dilute nitric acid, likewise, precipitates the dyspeptone, but the 

 precipitate is far more soluble in excess of the acid. On w^arming the" 

 acid solution, it quickly turns yellow, and with ammonia gives the 

 orange yellow color of the xanthoprotein reaction. 



Cupric sulphate and potassium hydroxide give the violet color of 

 the biuret reaction. 



Cupric sulphate and ferric chloride both give heavy precipitates, 

 insoluble in excess. 



Potassium hydroxide and lead acetate give, on boiling, a distinct 

 reaction for sulphur. 



Mercuric chloride, added in small quantity to a cold aqueous solu- 

 tion of the dyspeptone, gives no precipitate, but when added in 

 excess and the mixture is heated, a heavy white i^recipitate is formed, 

 insoluble on cooling. 



The dyspeptone is precipitated by saturation of its aqueous solution 

 with ammonium sulphate, but not by sodium chloride, even on heat- 

 ing. Addition of acetic acid, however, to the salt-saturated fluid 

 gives the usual precipitate of dyspeptone. 



Casein antialbumid. 



On heating casein with sulphuric acid and water at 100° C, it is 

 decomposed, as is well known, into soluble products and an insoluble 

 antialbumid. We have found, however, that the antialbumid pre- 

 pared in this manner is quite difierent in composition from the dys- 

 peptone formed in gastric digestion. In one experiment, where about 

 two kilograms of pure, moist casein were heated with two litres of 

 water and 100 grams of concentrated sulphuric acid for seven hours 



