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



The Lability of Caseinoycn. 



The first experiments on milk clotting were directed towards a preparation 

 ■of a standard caseinogen solution, upon which the action of alkalis could be 

 quantitatively studied. Tor the preliminary investigations, two different 

 samples were employed, viz., a commercial preparation made by the 

 Khenania " factory of Aix-la-Chapelle, and a preparation made in the 

 laboratory by a slight modification of Hammarsten's process. 



The Solubility of Caseinoyen in Alkalis. 



It has been long known that caseinogen can dissolve in alkalis to give rise 

 to highly acid solutions of what are presumably acid salts. The degree of 

 solubility in alkaline solutions was employed throughout these researches to 

 characterise the various preparations. 



In the determination of this factor, no pretence can be made to the 

 ■accuracy which can be attained in the estimation of the solubility of crystalline 

 substances, owing to various inherent experimental difficulties. The alkaline 

 solution most generally employed was that of saturated calcium hydroxide 

 diluted with its own volume of freshly boiled water (h sat. Ca(OH) 2 ). An 

 excess of the caseinogen preparation (usually 1*5-2 grin.) was mixed with 



20- 25 c.c. of the lime water solution in a bottle, which was then placed over 

 night (usually about 17 hours) on a rotating axis in a thermostat kept at 



21 - 5° C. At the end of this period a saturated solution of caseinogen in lime 

 water containing the excess of undissolved caseinogen was obtained. This 

 mixture could not be directly filtered in the thermostat, as the pores of the 

 filter soon become clogged. In order to get a filtrate, the mixture had to be 

 submitted to prolonged centrifugalisation. An attempt was made to work in 

 ■every case under as nearly as possible the same conditions. The mixture was 

 consequently always centrifuged for two hours at a speed of 3500 revolutions 

 per minute. After this treatment, the supernatant fluid could be readily 

 filtered through small folded filters. The defects of this method are obvious. 

 It is impossible to work under absolutely constant conditions, and the liquid 

 becomes slightly warm as the result of the centrifugalisation. As there is 

 evidence that the calcium salt of caseinogen undergoes hydrolysis readily 

 when solutions diluter than half- saturated lime water are employed as a 

 solvent, it can be readily understood that errors can arise from the want of 

 constancy of temperature throughout the whole experiment due to the 

 impossibility, with the laboratory appliances available, of carrying out all 

 investigations at exactly the same temperature. Furthermore, the alkaline 

 solutions employed are very dilute, and a relatively small error in standardising 



