CASEOSES. 36 



absolutely correct, but probable near approximations. They 



are : — 



Curd, . . . . Ci«H^,N3,SP0„ 



\\ liey caseose, Cy,H5.N,-,0„ 



The curd produced by rennet (calculated for 0-477 casein 

 nitrogen, cj. p. 30) contains : — 



Calculated. 

 Nitrogen, . . . 0-411 0-419 



CaO, . . . . 0-119 0-119 



PA 0-117 0-121 



Ash, 0-2.3 0-24 



and the quantity of caseose nitrogen left in the whey is 



0-061 0-0.58 



The acidity of the whey was found to be 8-4 c.c. of normal 

 alkali per litre less than that of the milk. 



These figures are in accordance with the view that casein in 

 milk, Ci,;oH^,-,^N^jSPOjoCaNa . J(Ca;,PoOy), is split by rennet into — 



C„„H.„„N:„i8P0,^Ca . -MCajP^Og) (curd) 

 and CjjH .^N.-.O,,! (whey ca.seose). 



The whey caseose is free from tyrosine and tryptophane. When 

 acted on by lactic acid the curd protein forms lactates, which have 

 the property of becoming strinji;y when heated. 



If calcium be removed from milk the action of rennet differs, 

 and a whole series of caseoses is formed, and no curd is produced. 

 Casein and its immediate derivatives appear to have the power 

 of forming with tricalcium phosphate very insoluble salts. 



Reactions of the Caseoses. 



Dys-caseoses. — These products in the pure state are soluble 

 in water ; they combine with calcium salts, especially phos- 

 phates, to form insoluble compounds. 



The following reactions are given by dys-pepto-easeose ; the 

 other dys-caseoses behave similarly. 



Acetic acid in moderate excess gives an insoluble white pre- 

 cipitate, soluble in large excess on heating. 



Hydrochloric and sulphuric acid give precipitates, also soluble 

 in large excess on heating. Even 0-2 per cent, hydrochloric acid 

 produces complete precipitation. 



Nitric acid gives a precipitate far more easily soluble in excess 

 of acid. On warmins, the solution turns yellow, and, with 

 ammonia, gives the orange-yellow colour of the xantho-proteiu 

 reaction. 



With a little copper sulphate and an excess of caustic potash 

 the violet colour of the biuret reaction is given. 



