1913.] 



Phenomena of" Clot " Formations. 



475 



of the number 17 or 18, which would have been expected, had the solubility 

 been one-half of that in \ sat. Ca(OH) 2 . As these figures indicate hydrolytic 

 dissociation of the calcium salt in low dilutions, it is not unreasonable to 

 suppose that the saturated solution of caseinogen in \ sat. Ca(OH) 2 undergoes 

 a similar hydrolysis when the temperature is raised.* Xow attention has 

 been called to the fact that calcium chloride does not produce a clot with 

 calcium caseinogenate at room temperature, but only when the mixture is 

 slightly wanned (e.g. to 25°). If, however, the calcium caseinogenate is first 

 treated with carbon dioxide gas, which produces by itself no precipitate, the 

 subsequent addition of calcium chloride rapidly produces a clot in the cold. 

 Finally, it is possible to produce a clot from sodium caseinogenate solutions 

 in the absence of calcium salts. Rennet by itself produces no clot from 

 such solutions ; if, however, they are treated first with carbon dioxide, the 

 addition of the ferment solution causes clot production after a short interval, 

 even in the cold. There is evidence that the sodium salt does not readily 

 undergo hydrolytic dissociation (see table on p. 464). Carbon dioxide can 

 apparently decompose the sodium salt and set free sufficient free caseinogen 

 to allow the clotting process to take place. 



Saturated solutions of metacaseinogen (prepared by the treatment of 

 '■' natural " caseinogen with water for 24 hours at 37°) in £ sat. Ca(OH) 2 do 

 not clot on the addition of rennet, and yield only a very faint precipitate on 

 addition of the ferment after previous treatment with carbon dioxide. The 

 action of calcium chloride on these solutions has been already described. By 

 means of these reactions, metacaseinogen can be readily distinguished from 

 caseinogen. 



Caseinogen, after solution in alkalis and reprecipitation with acetic acid, 

 can yield solutions in -|- sat. Ca(OH) 2 , which clot on the addition of rennet or 

 calcium chloride. Furthermore, clots can be produced by the same method 

 from metacaseinogen which has been reconverted into caseinogen by treat- 

 ment with alkalis (with the usual precautions), provided that the former has 

 not been changed too much by very prolonged action of water either at 37° 

 or at higher temperatures. Where such additional changes have been 

 brought about, there is evidence of the partial scission of phosphoric acid 

 from the caseinogen molecule. In no case was it found possible to reconvert 

 a metacaseinogen into a caseinogen with quite as high a solubility in 

 J sat. Ca(OH) 2 as "natural" caseinogen. Alkali appears, therefore, to exert 

 some slight subsidiary action. 



Cf. Brailsford Robertson. 



VOL. LXXXVI. — B. 



2 N 



