DETECTION OF PHOSPHORUS COMPOUNDS. 6 1 



centration of o. I per cent, will proceed in the presence of nitric 

 acid having a concentration sufficient to prevent reduction in a 

 solution of ammonium molybdate of 2 per cent, strength. 



While it would have been difficult to draw from these experi- 

 ments conclusions as to the probable behavior of the compounds 

 of molybdic acid in the tissues when treated with solutions of 

 phenylhydrazin hydrochloride containing nitric acid, yet they 

 suggested a possibility which was capable of being proved experi- 

 mentally that the compounds of molybdic acid and molybdates 

 found in the tissues would fail to react to phenylhydrazin hydro- 

 chloride in the presence of an amount of nitric acid which would 

 have no effect on the reduction of ammonium phosphomolybdate. 



In order to test this question, sections of the liver of Necturus 

 prepared after fixation in alcohol and fastened to the slide by the 

 water method were treated with Macallum's nitric molybdate re- 

 agent, a solution of soluble molybdic acid in 10 per cent, nitric 

 acid, and a ten percent, solution of phosphoric acid, respectively. 

 The two first mentioned solutions were allowed to act for three 

 hours at 37.5 C. followed by eighteen hours at ordinary room 

 temperature. They were then tested with a o. I per cent, solution 

 of phenylhydrazin hydrochloride and found in each case to give a 

 strong reaction corresponding in its characters and distribution 

 to the phosphorus reaction of Macallum. The reaction obtained 

 in the sections treated with the solution of molybdic acid was much 

 the stronger. Other sections from the same lot were then treated 

 with solutions containing o. I per cent, of phenylhydrazin hydro- 

 chloride and varying known quantities of nitric acid, in each case 

 for a period of fifteen minutes. The sections from the molybdic 

 acid solution and from the nitric molybdate reagent were treated 

 side by side in the same solution, and for purposes of control a 

 section which had been soaked in phosphoric acid and then treated 

 with the nitric molybdate reagent was also put at the same time 

 in the solution, so that it was possible to observe the effect of 

 different concentrations of nitric acid on the reduction of sections 

 treated with molybdic acid, or with the nitric molybdate reagent, 

 and of sections containing ammonium phosphomolybdate arti- 

 ficially introduced. It was my expectation that a low concentra- 

 tion of nitric acid would suffice to abolish that portion of the reac- 



