[Reprinted from the Journal of Physiology. 

 Vol. XXXV. Nos. 1 & 2, December 1906.] 



ON METHODS SUPPOSED TO LOCALIZE PHOSPHORUS 

 IN CELLS. BY F. H. SCOTT, Pn.D., M.B., Mackinnon 

 Research Student. 



(From the Physiological Laboratory of University College, London.) 



Introduction. The various tests for phosphorus which have been 

 proposed depend on the use of a solution of ammonium molybdate in 

 nitric acid. It has been assumed that the nitric acid would liberate 

 the phosphorus from its organic combinations ?s orthophosphate, and 

 that this would then be precipitated as ammonium phosphomolybdate. 

 To distinguish the yellow precipitate from the yellow colour produced by 

 the action of the nitric acid on the proteid, agents have been employed 

 to reduce the phosphomolybdate to one of the coloured oxides of 

 molybdenum. The dark coloration obtained in this way was considered 

 to indicate the presence of phosphorus. 



Lilienfeld and Monti (1 >, who were the first to try to localize the 

 compounds of phosphorus in cells, after first treating the tissues with 

 the nitromolybdate reagent then treated them with a solution of 

 pyrogallol, which turned parts of the tissue yellow, brown or black. 

 These colours were believed to indicate the presence of phosphorus. 

 Ra9iborski w , in a criticism of Lilienfeld's and Monti's work, pointed 

 out that pyrogallol, both in the test tube and in tissues, reduces 

 ammonium phosphomolybdate to the blue oxide of molybdenum while 

 it blackens ammonium molybdate. He therefore regarded Lilienfeld 

 and Monti's results (yellow, brown or black) as due to the reduction of 

 ammonium molybdate which had not been washed from the tissues 

 He also pointed out that the nitromolybdate reagent will not react 

 with nuclein compounds even after 48 hours, while on the other hand 

 these nuclein compounds have a great power of retaining ammonium 

 molybdate and are therefore blackened on subsequent treatment with 

 pyrogallol. The same affinity of nucleins for ammonium molybdate was 

 independently pointed out by Gilson (3 >. 



