458 R. H. A. PLIMMER AND W. M. BAYLTSS. 



50 c.c. precipitated by tannic acid and oxidised by Neumann's method <tc. gave 

 20-79 mgm. P 2 3 . 



50 c.c. contained (i.e. 10 c.c. oxidised directly by Neumann's method, &c.) 20-92 nigm. 

 P 2 5 



i.e. the total phosphorus was present in a soluble form. 



50 c.c. precipitated by magnesium citrate gave 6-59 mgm. ) _ _ , , ,, n 



,* 111GQH I J. J. 11)11111. A ()\JK 



50 c.c. ,, ,, 7-64 i 



The inorganic phosphoric acid was completely precipitated, as was shown by the 

 following experiments where 10 c.c. standard acid potassium phosphate were also added : 



50 c.c. + 10 c.c. KH 2 PO 4 solution precipitated by magnesium citrate gave 27 '64 mgm. ) mean = 27-45 mgm. 

 50 c.c. + 10 c.c. KH 2 P0 4 27-26 mgm. i P A 



i.e. 50 c.c. gave 7'45 mgm. P 2 5 . 



Thus, by the action of trypsin on caseinogen, the whole of its 

 phosphorus is not split off as in organic phosphoric acid but only 35 

 per cent. This value is 8 per cent, higher than that obtained by Biffi, 

 but the discrepancy in the values can be accounted for by the length of 

 time of the digestion, which, in our experiment, was considerable. 



Since 1 per cent, alkali separated the whole of the phosphorus of 

 caseinogen as inorganic phosphoric acid and trypsin only 35 per cent, 

 the question arose, Will 1 per cent, caustic soda convert the remaining 

 65 per cent, of the soluble P 2 O 5 , i.e. the phosphorus contained in organic 

 combination of a trypsin-caseinogen digestion, into inorganic phosphoric 

 acid ? To determine this, to 200 c.c. of the above trypsin digest were added 



N 

 100 c.c. water and 100 c.c. NaOH solution. These quantities bring 



the percentage of alkali to 1 per cent. A precipitate was obtained on 

 adding the caustic soda ; this was filtered off and the clear filtrate was 

 kept at 38 C. for 40 hours and then examined for inorganic phosphoric 

 acid : 



50 c.c. precipitated by magnesium citrate gave 4-95 mgm. ) mean = 5'26 mgm. \ 



50 c.c. ,, 5-58 j P A 



50 c.c. + 10 c.c. KH 2 P0 4 solution precipitated by mag- \ 1 mean = 5-03 mgm. 



nesium citrate gave 24-34 mgm. mean = ^2^5 



50 c.c. + 10 c.c. KH 2 P0 4 solution precipitated by mag- 24-91 mgm. 



nesium citrate gave 25-48 mgm. J / 



i.e. 50 c.c. gave 4-91 mgm. P 2 5 . 



The original solution was diluted by an equal volume of water and 

 alkali; 2x5'03 = 10'06 mgm. P 2 O 5 are therefore precipitated after the 

 action of 1 per cent, caustic soda, an increase of 10*06 7 '45 = 3'61 mgm. 

 This corresponds to 50 per cent, of the total soluble P a O 5 . 



