48 Gooch and Curtis — Halogen Acids upon Vanadic Acid. 



the condition of the trioxide without the addition of phos- 

 phoric acid. In fact, the presence of phosphoric acid may 

 work disadvantageously when low volumes are reached by per- 

 mitting a dangerous rise of temperature in the still liquid resi- 

 due. This is shown in the following series of experiments in 

 which 1 gm. of potassium iodide, 2 cm3 of . syrupy phosphoric 

 acid (sp. gr. l'TO) and 0*1 gm. ammonium vanadate were 

 treated, the initial volume being 60 cm3 . 



Table V. 





In 0-1000 NH 4 V0 3 















tal 



en 





Eeduction flask 



Eeceiver 



Exp. 







Final 

























V 2 4 



v 2 o 3 



vol. 



As 



As 



As 



As 





gm. 



gm. 



cm 3 . 



v 2 o 4 



V 2 3 



v 2 o 4 



v 2 o 3 



1 



0699 



0632 



35 



0-0693 





0-0698 





2 



0-0699 



0-0632 



25 



0-0705 





0-0711 





3 



0-0699 



0-0632 



22 



0-0711 





0-0706 





4 



0-0699 



0-0632 



4 



» « _ * 



0-0606 



.... 



0-0623 



5 



0-0699 



0-0632 



2 







* 







00617 



6 



0-0699 



0-0632 



2 



. - - - 



0-0597 



— • - • 



0-0612 



7 



i)-0699 



0-0632 



1-7 



.... 



0-0621 



* - — * 



0-0613 



8 



0-0699 



0-0632 



1-6 





* 







0-0624 



9 



0-0699 



0-0632 



1-4 







0-0604 







0629 



These figures indicate also that when the distillation is 

 continued until the volume is about 35 cm3 , the condition of 

 oxidation corresponds nearly to that of the tetroxide. When 

 the residue is concentrated almost to dryness, the figures 

 approach the value for the trioxide, but under the conditions 

 they are of doubtful value ; for, fumes of hydriodic acid are 

 visible in the flask, more or less spattering occurs, and the 

 temperature is such that a volatile compound of vanadium 

 begins to distil. 



In summary of the work described it may be pointed out 

 that in the interaction of hydrochloric, hydrobromic, and 

 hydriodic acids upon vanadic acid the degree to which the 

 last is reduced depends, as would be expected in reversible 

 reactions, upon the concentrations. It has been shown that 

 hydrochloric acid is capable of carrying the reduction, even in 

 the cold, to the condition of the tetroxide, and under none of 

 the conditions tried does reduction go further : that hydro- 

 bromic acid, which in small concentrations gives a definite 

 reduction to the condition of the tetroxide, may easily push 

 the reduction well on toward the condition of the trioxide : 

 that the reduction by hydriodic acid may be carried at will 

 to either of the stages — that of the trioxide or that of the 

 tetroxide. 



* Flask broke. 



