448 72. //. A. PLIMMER AND W. M. BAYLI8S. 



Investigations have also been made on the chemical nature of the 

 soluble P 2 O 5 ; these will be described more conveniently later. 



B. Separation by Pepsin. A great deal of work has already been 

 done upon the behaviour of the phosphorus of caseinogen, when this 

 substance is submitted to the action of pepsin. Moraczewski* 6 ', 

 Sebelien (2) , and Salkowski (4) > (5) ' (7 >, have each shown that except for a 

 small residue the whole of the phosphorus passes into solution, but they 

 made no determinations with regard to the rate of its solution. We 

 have therefore made investigations upon this point, and have employed 

 the same method as above described with trypsin, using tannic acid as 

 precipitant and estimating the P 2 3 in the filtrate. In the earlier 

 experiments the caseinogen was simply suspended in 0'4 per cent, 

 hydrochloric acid solution, but, in the later Experiments, 3, 4, 5, the 

 caseinogen was previously dissolved in the amount of alkali recom- 

 mended by Salkowski (13) . In this way lumps of caseinogen were 

 avoided, as it is reprecipitated, on acidifying in a fine state of division, so 

 that, according to Salkowski, it can pass completely into solution under 

 the most favourable conditions. Using this method we found that a 

 greater quantity of the phosphorus went into solution, and also that its 

 solution was more rapid. The following are the data which were 

 obtained : 



(1) 20 grs. caseinogen; 0-1 gr. pepsin. (2) 20 grs. caseinogen; O'l gr. pepsin. 



1000 c.c. 0-4 per cent. HC1. 1000 c.e. 0-4 per cent. HC1. 



Soluble P 2 O 5 Soluble P 2 O 5 Soluble P 2 O 5 Soluble P a O 5 



Time in mgni. 



6-3 

 30 mins. 5'4 



1 hour 6-0 



2 hours 5-9 

 4 6-0 



Total 34-2 I Total 34-2 



The splitting-off of the phosphorus was in all cases very slow, but its 

 rate was quite regular and comparable to that obtained by other observers 

 on enzyme action. The whole of the phosphorus never passed into the 

 soluble form. Even after 149 days' digestion the quantity dissolved was 

 only about of the total phosphorus (Experiment 4) ; in Experiment 5 

 the quantity was about T 7 ^ or rather less. This was probably due to the 

 difference in the amount of acid employed, the larger quantity in 

 Experiment 4 having possibly a slight effect in the prolonged digestion. 

 The ratio of soluble nitrogen to total nitrogen was also determined in 



