DETECTION OF PHOSPHORUS. 121 



persulphate also added. The mixture should be allowed to stand for 

 some time in order to allow any phosphate, which may be present 

 in the reagents, to be precipitated. 



The above reagent is as sensitive as the nitromolybilate reagent and 

 will give an undoubted reaction with as little as '005 tngrn. of sodium 

 phosphate. The addition of an oxidizing agent (persulphate, hydrogen 

 peroxide, chromic acid) is only necessary when the reageut is to be 

 applied to tissues, but without such oxidizing agent the tissues will turn 

 blue owing to the reduction of the molybdic acid. (Bensley observed 

 the same for a solution of molybdic acid in hydrochloric acid.) 



Sections of alcohol hardened material may be left in this reagent for 

 days at 37, and if they have been properly freed from inorganic 

 phosphate no yellowing of the tissue is seen. Sections of testis (frog) 

 were chiefly used in this work but sections of bone marrow, liver, 

 pancreas and cerebellum were also tried. The nuclei of the fresh blood 

 corpuscles of the newt do not turn yellow in this reagent even after 



4 or 5 days. The same absence of effect is noticed if instead of sections 

 small pieces of tissue are taken. If these have been freed from inorganic 

 phosphate they do not show any yellow coloration, but if they contain 

 inorganic phosphate they give an immediate reaction. Even lecithin 

 compounds do nut give a reaction (turn yellow) either with the nitro- 

 or the hydrochloric molybdate reagent. If, however, small masses of 

 lecithin are put in either of these reagents one rinds after a few days 

 a crop of pbosphomolybdate crystals on the sides of the flask. This 

 shows there is no localizing action, and that even from such compounds 

 as lecithin the first effect of the reagent is to liberate some soluble 

 compound of phosphorus which, however, is nob acted upon by the 

 reageut until it is further hydrolysed. Lecithin may be boiled with 

 acids on a water bath and, unless the hydrolysis be continued for 4 or 



5 hours, no inorganic orthophosphate is formed. 



The reason for the absence of results with these micro-chemical 

 reagents has been found by a study of the hydiolysis of tissues with 

 acids at various temperatures. This work has been done in conjunction 

 with Dr R H. Aders PI i miner who has kindly allowed me to make use 

 of these results. The method followed was that used by Bayliss 

 and Plimrner' 9 ' in their work on the liberation of phosphorus from 

 caseinogen. The acid was a'lded to the ground tissue (ox testis), 

 thoroughly mixed, and then a sample (50 c.c.) withdrawn in a pipette 

 and dropped into 50 c.c. of taunic acid reagent (Cathcart's (10) formula 

 + an equal volume of water) and allowed to stand till the next day 



