468 



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



The " natural " caseinogen is therefore very unstable in the presence 

 of acids. 



This change in the caseinogen is not due to a ferment carried down with 

 it when it is precipitated from milk, as a product of high solubility in 

 alkali is also obtained when the milk is boiled before the precipitation of 

 the caseinogen. Some preliminary experiments, which need not be given 

 in detail here, indicate that substances present in the milk serum protect 

 the caseinogen from change, when treated with water. 



Action of Water on " Natural " Caseinogen. 



The action of water on " natural " caseinogen at various temperatures was 

 also investigated in some detail. The method of experiment was exactly 

 the same as that employed in the researches on the action of water on 

 caseinogen prepared by Hammarsten's method (see p. 465). The result of 

 the determinations of the solubility in |- sat. Ca(OH)2 of the various products 

 are indicated in the following table : — 



Solubility of Original Preparation, 35. 



Temperatures 



37°. 



75°. 



100°. 



Time of heating — 









£ hour 



16 -8 



17 -6 



14 -5 



1 „ 



17 -2 



18 -5 



13 -4 



2 hours 



14 -1 



13 -8 



11 '2 



5 „ 



14-7 



11 -f 



9 



10 „ 



13-4 



11 -8 



6-0 



26* „ 



11 -5 



10 -8 



4 9 



The changes at 51° did not differ materially from those at 37°. It will 

 be observed that up to 75° the temperature has but little effect on the rate 

 of change. Within the first half-hour, however, the caseinogen, even 

 at 37°, breaks down into a product with only about half the solubility of 

 the original preparation in \ sat. Ca(OH) 2 . At ordinary room tem- 

 perature the change is very slow, a preparation left in contact with water 

 for 24 hours having its solubility reduced only to about 30. It is not at 

 present possible to formulate the chemical changes which have been 

 described above. It seems, however, feasible to assume that they are 

 produced by the scission or addition of the elements of water. It is 

 advisable to recall the fact that water is necessary to produce these changes, 

 and the caseinogen itself remains unaltered on boiling with alcohol. If the 

 above conception is correct the presumably more complex and more soluble 

 caseinogen is a poly-acid which first undergoes hydrolysis into a simpler 



