476 



Mr. S. B. Schryver. Investigations on the [Mar. 6, 



The Chemical Nature of the Clot. 



As already stated, clots ; whether produced by calcium chloride alone, or by 

 rennet alone, can be distinguished from metacaseinogen or caseinogen pre- 

 cipitates by the fact that, when moist, they yield an indiarubber-like mass on 

 treatment with alcohol, whereas the unclottecl material undergoes no visible 

 change. 



A systematic examination was made of the clots prepared by various 

 processes with the object of determining their relationship to caseinogen and 

 metacaseinogen. The rennet clot was formed by adding 1 c.c. of a com- 

 mercial rennet solution to 50 c.c. of a saturated solution of "natural" 

 caseinogen in \ sat. Ca(OH)2- The mixture was made in a high cylinder in 

 the cold, and was then placed in an incubator. After about 10 minutes, the 

 whole had set to a solid clot, which was broken up, filtered off from the 

 liquid, washed with ice-cold water, alcohol, and ether, and then air-dried. It 

 was then boiled with absolute alcohol for about 10 minutes to destroy the 

 ferment, and analysed. A portion was then dissolved in weak sodium 

 hydroxide solution and reprecipitated, after filtration through pulp, by acetic 

 acid, rapidly washed with ice-cold water after precipitation, and freed from 

 water in the usual way. 



The clot produced by calcium chloride was prepared by mixing the calcium 

 caseinogenate solution with an equal volume of N/25 calcium chloride 

 solution, and incubating the mixture until the clot had formed. This was 

 then filtered off, washed with 50-per-cent. alcohol until the washings were 

 free from chlorine, then with absolute alcohol and ether, and then air-dried. 

 To free it from calcium it was treated in the same way as the rennet clot, i.e. 

 redissolved in alkali (NaOH), and reprecipitated with the usual precautions. 



It was found that the clots produced by rennet alone and by calcium 

 chloride alone differed in one important particular, for whereas the calcium 

 chloride clot (purified by solution in alkali and reprecipitation) gave with 

 -| sat. Ca(OH) 2 a milky solution of high solubility (more than 30), which 

 clotted on addition both of rennet and calcium chloride, the purified 

 substance from the rennet clot yielded with the lime water of the same 

 concentration only an opalescent solution (solubility 12 - 5), which gave 

 a precipitate with an equal volume of N/25 calcium chloride solution, and 

 no clot on addition of rennet. 



The rennet clot differed therefore both from metacaseinogen and caseinogen, 

 in that, even after re-solution in alkali, it no longer gave rise to a product 

 capable of giving with \ sat. Ca(OH) 2 an opaque highly concentrated 

 solution, from which clots can be formed. 



