6O R. R. BENSLEY. 



REACTIONS OF PHOSPHOMOLVBDIC ACID AND PHOSPHOMOLYB- 

 DATE OF AMMONIUM WITH PHENYLHYDRAZIN 

 HYDROCHLORIDE. 



Phenylhydrazin when added to a solution of phosphomolybdic 

 acid or to crystals of ammonium phosphomolybdate suspended in 

 water gives at once the reduction to the blue oxide. The reac- 

 tion under these conditions proceeds so rapidly that it is difficult 

 to follow the steps. The resulting body is not green in color as 

 described by Macallum but blue, the green color which is first 

 seen when phenylhydrazin hydrochloride is added to the crystals 

 of ammonium phosphomolybdate being simply due to the yellow 

 background afforded by the unreduced phosphomolybdate. 

 After a few minutes the reaction proceeds still further and a solu- 

 ble blue-violet compound is formed. 



In the presence of nitric acid, the reaction proceeds somewhat 

 more slowly, although it is less sensitive to the presence of nitric 

 acid than the corresponding reactions with molybdic acid and 

 ammonium molybdate. With crystals of phosphomolybdate sus- 

 pended in water and o. I per cent, of phenylhydrazin the concen- 

 tration of nitric acid may be increased to 36 per cent, without the 

 reduction to the blue oxide being prevented. Even in the pres- 

 ence of this great amount of nitric acid the reduction of the 

 phosphomolybdate reaches a maximum within ten minutes after the 

 phenylhydrazin hydrochloride is added. The reaction between 

 phenylhydrazin and phosphomolybdic acid proceeds in much 

 the same way, and is similarly much less sensitive to the 

 presence of nitric acid, than the corresponding reactions with 

 molybdic acid and ammonium molybdate. For purposes of 

 comparison the experiments were made the results of which are 

 presented in the subjoined table. 



Percentage of Phosphomolyb- Percentage of Phenylhydrazin Per Cent. Nitric Acid Necessary 

 die Acid. Hydrochloride. to Prevent Blue Reaction. 



o.i o.i 6.55 



O.2 O.I 9.82 



0.3 o.i 13.10 



0.4 o.i J4-74 



On comparison of this table with the preceding one it will be 

 seen that the reduction of phosphomolybdic acid having a con- 



