D. L. Randall — Behavior of. Molybdic Acid. 



515 



tor in succession 100 cm3 of hot dilute sulphuric acid (2*5 per 

 cent), the ammonium molybdate dissolved in 10 cm3 of water and 

 acidified with 100 cra3 of the hot dilute acid (2 - 5 per cent), 

 200 cmS of the hot dilute acid and finally 100 cm3 of hot water. 

 The solution was titrated while still hot with approximately 

 tenth normal permanganate standardized against ammonium 

 oxalate. 



The molybdenum as it passed through the lower part of the 

 reductor was green, but on coming in contact with the ferric 

 salt was changed to a bright red color. The results in the fol- 

 lowing table are calculated on the assumption that the molyb- 

 denum was reduced to the form of Mo 2 3 . The close 

 agreement with theory indicates that the recluctor is able to 

 reduce molybdenum to that form and that the reduction does 

 not stop at a point represented by the formula Mo 24 37 or 

 Mo 12 19 . 



Table III. 



Ammonium 















molybdate 



Iron 





KMn0 4 



MoO 







taken 



sol. 



H 3 P0 4 



used 



found 



theory 



Error 



grams. 



cm 3 . 



cm 3 . 



cm 3 . 



grms 





grms. 



•2000 



20 



4 



30-38 



•1628 



•1631 



— •0003 



.2000 



20 



4 



30.45 



•1632 



•1631 



+ .0001 



•2000 



20 



4 



30-33 



•1626 



•1631 



— •0005 



•3000 



30 



4 



45-65 



•2447 



•2447 



±'0000 



•3000 



30 



4 



45-80 



•2455 



•2447 



+ 0008 



•3000 



30 



4 



45-73 



•2451 ■ 



•2447 



+ •0004 



•3000 



30 



4 



45-76 



•2453 



•2447 



+ •0006 



•3000 



30 



4 



45-68 



•2448 



•2447 



+ -oooi 



•3000 



30 



4 



4564 



•2446 



•2447 



— •0001 



•3000 



30 



4 



45-71 



•2449 



•2447 



+ •0002 



It having been shown that molybdenum may be successfully 

 and uniformly reduced to the condition of Mo„0 3 by anticipa- 

 ting any previous action of air and registering the oxidation 

 by the action of a ferric salt, the method was then applied to 

 the determination of phosphorus in ammonium phospho- 

 molybdate precipitated in the usual manner. 



For this work a solution of microcosmic salt was made up 

 1'2 grams to the liter and the phosphorus content determined 

 by evaporating 50 cm3 in a platinum crucible and igniting to form 

 the sodium metaphosphate. 



With the exception of using an equivalent amount of ammo- 

 nium molybdate instead of molybdic anhydride, the method 

 given by Blair* was used for making up the molybdate reagent. 

 According to this method, 100 grams of pure molybdic anhy- 

 dride and 400 cm3 cold distilled water are thoroughly mixed and 

 the mixture is treated with 80 om3 of strong ammonia (0*90 

 sp. gr.). When the solution is complete, the liquid is filtered 



* Chem. Analysis of Iron, vi ed., p. 97. 



