DETECTION OF PHOSPHORUS COMPOUNDS. 51 



to the strength of the solution. On a solution of the molybdate 

 containing nitric acid, c. g., that used as the reagent for phos- 

 phoric acid, it had no apparent effect on the molybdenum com- 

 pound, although, in a few minutes, a soluble, reddish, aromatic 

 compound might be formed in the solution. On the other hand, 

 with phosphomolybdates, either in the presence or in the absence 

 of ammonium molybdate, or of nitric acid, or of both, it gave at 

 once the dark green oxide of molybdenum. 



Concerning the use of these reagents on tissues Macallum 

 says: " On the molybdate and phosphomolybdate compounds 

 distributed in animal and vegetable tissues, the phenylhydrazin 

 hydrochloride acts as it does on these in the test-tube. It is not 

 necessary to free the tissue preparations from ammonium molyb- 

 date." He recommends washing the preparations for a minute 

 or two in a dilute solution of nitric acid after which they are 

 transferred to the reducing solution, which in less than two min- 

 utes, brings out the green color where the phosphomolybdate 

 compound occurs, but a faint yellow reaction where ammonium 

 molybdate alone is present. 



The technique of the reaction is as follows: Fresh tissues or 

 tissues hardened in alcohol were used. Pieces of tissue or thin 

 sections in the case of hardened material, were placed, for a 

 period varying from ten minutes to forty-eight hours, in a solution 

 of ammonium molybdate in nitric acid, prepared by dissolving 

 one part of pure molybdic acid in four parts of strong ammonia, 

 and adding thereto, slowly, fifteen parts of nitric acid, sp. gr. 1.2. 

 After the nitric molybdate reagent has acted for a sufficient 

 length of time, the preparations are washed in water or in dilute 

 nitric acid, and treated with a ^ per cent, solution of phenyl- 

 hydrazin hydrochloride, which reduces the phosphomolybdate to 

 a -green-colored oxide of molybdenum. 1 The tissues may be 

 then dehydrated, cleared in. oil of cedar and mounted in 

 balsam. 



According to Macallum, inorganic compounds of phosphorus 



'Although Macallum speaks of a green oxide of molybdenum being formed by this 

 reaction, it is probable that the bodies formed belong to the blue oxides. The green 

 color obtained at the beginning of the reduction of phosphomolybdate of ammonium 

 in vitro is due to the yellow background of unreduced molybdate, that obtained in 

 the tissues to the associated xanthoproteic reaction (vide infra). 



