60 PROTEINS. 



The insoluble compound with lime salts is dissolved with more 

 or less readiness by an alkaline trypsin solution, giving finally 

 a caseone, presumably trypto-caseone. 



Proto-caseoses. Proto-caseoses are soluble in water, and 

 precipitated incompletely by the addition of acetic, hydrochloric, 

 sulphuric, and nitric acids. They are soluble in 04 per cent, 

 hydrochloric acid, but are precipitated by stronger solutions. 

 The portion not precipitated by acetic acid gives a precipitate 

 on saturation with salt solution and with potassium ferrocyanide. 



Copper sulphate gives a heavy precipitate, as does ferric 

 chloride, but the latter is soluble in excess of the reagent. They 

 give the xantho -protein reaction with nitric acid. 



Proto-caseoses are precipitated by saturation with sodium 

 chloride. 



a-Deutero- Caseoses are soluble in water, not precipitated by 

 acids nor by saturation of a neutral solution with sodium chloride ; 

 on adding acetic acid to the salt-saturated solution, a-deutero- 

 caseose is incompletely precipitated ; it is precipitated by satu- 

 ration with ammonium sulphate in the cold. 



/?-deutero-caseose is precipitated by saturation of the solution 

 with ammonium sulphate and boiling. 



Cupric sulphate gives a precipitate with a-deutero-caseose 

 soluble in excess, but none with /?-deutero-caseose. 



Potassium ferrocyanide in acetic acid solution gives a preci- 

 pitate with both deutero-caseoses. 



Caseone. Only the trypto-caseone has been prepared ; it is 

 not precipitated by acids ; nor by saturation of its solution by 

 sodium chloride ; nor by ammonium sulphate, even on boiling ; 

 nor by zinc sulphate. Caseone and peptones generally are very 

 hygroscopic. Caseone is dialysable and only precipitated by 

 such reagents as tannin and phospho-tungstic acid. 



All the caseoses and caseones give the biuret reaction with 

 copper sulphate and caustic potash. 



It must be remembered that the separation of the caseoses is 

 by no means sharp ; thus proto-caseose is not completely preci- 

 pitated by sodium chloride and the residue is obtained with the 

 a-deutero-caseose . 



Besides the above products another caseose, resembling proto- 

 caseose, but soluble only in dilute acid and salt solutions, is 

 also formed ; this is called hetero -caseose and is precipitated by 

 dialysis. 



Lactalbumin. This protein has the property characteristic 

 of albumins of being coagulated by raising the temperature of 

 its solution to 70 C. ; the precipitation is never complete, since 

 as much as 12 per cent, may be left in solution, according to 

 Sebelein. 



