76 S. E. Moody — Hydrolysis of Ammonium Molybdate. 



Art. VIII. — The Hydrolysis of Ammonium Molybdate in 

 the Presence of Iodides and Iodates ; by Seth E. Moody. 



Glassman* makes the statement that ordinary ammonium 

 molybdate is hydrolyzed according to the following equation : 



3(NH 4 ) 6 Mo 7 24 .4H 2 = 9(NH 4 ) 2 Mo0 4 + 12H 2 MoQ 4 



and. that the molybdic acid thus set free reacts with a mixture 

 of potassium iodide and potassium iodate, liberating iodine 

 according to the equation : 



]2H 2 MoO 4 + 20KI + 4KIO 3 = 12K 2 MoO 4 + 12l 2 + 12H 2 O. 



The elimination of the iodine was accomplished by means of a 

 Bunsen's distilling apparatus and standard sodium thiosulphate 

 was used for its measurement. 



In a previous articlef the writer showed that certain salts of 

 ammonium may be completely hydrolyzed in the presence of a 

 mixture of potassium iodide and potassium iodate and that the 

 iodine liberated in the reaction between the freed acid and the 

 mixture may be eliminated and transferred in a current of 

 hydrogen to a receiver charged with potassium iodide and there 

 measured with a standard solution of sodium thiosulphate. It 

 was discovered that in the direct distillation of the iodine, 

 ammonia passes simultaneously into the receiver and there acts 

 upon some of the free iodine ; but that loss of iodine may be 

 obviated by first passing the gaseous products through hot 

 standard sulphuric acid, which holds the ammonia while allow- 

 ing the iodine to pass uncombined into the receiver. 



Similar experiments upon ammonium molybdate have now 

 been carried out by the method and with the apparatus formerly 

 described. It appears that, as in the case of the salts previously 

 examined, iodine may be set free in amount indicating the 

 complete hydrolysis of this salt, but that unless special pre- 

 cautions are taken the ammonia likewise liberated acts upon a 

 portion of the iodine and so falsifies the indication of hydrolysis. 



Table I shows results of experiments carried out according 

 to the method of Glassman, except that the distillation apparatus 

 consisted of a Voit flask used as a retort, a Drexel bottle used 

 as a receiver, and that a current of hydrogen was sent cautiously 

 through the apparatus. 



These results, taken by themselves, wouldjappear to show 

 that hydrolysis of the ammonium molybdate in the receiver 

 had taken place to about the degree indicated by Glassman's 

 equation ; but the liberation of more iodine upon acidifying the 

 solution after titration with sodium thiosulphate shows that 



*Ber. 1905, 38, I, p. 193. f This Journal, xxii, p. 379, 1906. 



