44 Gooch and Curtis — Halogen Acids upon Vanadic Acid. 



bonate (in solution 1 : 5), adding an excess of twentieth normal 

 iodine, allowing the mixture to stand twenty minutes (all with- 

 out admission of air) then transferring to a larger flask, intro- 

 ducing a slight excess of twentieth normal arsenious acid, and 

 titrating to standard blue with iodine. 



In experiment (7) the aqueous hydrobromic acid was strength- 

 ened by cooling and passing in gaseous acid before boiling ; and 

 in experiment (8) the residue in the flask was submitted to 

 several treatments of cooling, recharging with the vapor lib- 

 erated by heating the strong aqueous hydrobromic acid, and 

 boiling, in order to see the effect of varying the concentration, 

 the bromine evolved by each boiling being determined, and 

 finally the degree of reduction of the residue was estimated as 

 usual. The results of these experiments are calculated upon 

 the hypotheses that the vanadic acid is reduced (first) to the 

 tetroxide, (second) to the trioxide, and (third) that the trioxide 

 and tetroxide are left in mixture. 



Table II. 











| 



Found ; calc. as 





In 0-1000 N 



Found ; 



calc. as Found ; calc. as 



mixture from 



Exp. 



v,o 4 



en 



v 2 o 3 



v 2 o 4 



V 2 3 



figs, for receiver 



Flask 



Receiver 



Flask 



Receiver 



v 2 o 4 



V 2 3 





gm. 



gm. 



gm. 



gm. 



gm. 



gm. 



gm. 



gm. 



1 



0-0699 



0-0632 



00913 



0-0877 



0-0413 



>0396~ 



0-0521 



0-0160 



2 



0-0699 



0-0632 



0-0879 



0-0885 



0-0397 



0-0400 



0-0513 



0-0168 



3 



0699 



0-0632 



0-0849 



0-0896 



0-0384 



0-0405 



0-0502 



0-0179 



4 



0-0699 



0-0632 



0-0858 



0-0849 



0-0388 



-0-0384 



0-0549 



0-0136 



5 



0-0699 



0-0632 



0-0854 



0-0853 



0-0386 



0-0385 



0-0545 



0-0139 



6 



0-0699 



0-0632 



0841 



0-0839 



0-0380 



0-0379 



0-0559 



0-0127 



7 



0-0699 



0-0632 



0-0945 



0-0943 



0-0427 



0-0426 



0-0455 



0-0221 



8a 



0-0699 



00632 





0-0860 





0-0389 



0-0538 



0146 



86 









0-1104 





0-0499 



0-0295 



00366 



8c 









0-1291 





0-0584 



0-0107 



0-0535 



U 







0-1258 



0-1291 



0-0569 



0-0584 



0-0107 



0535 



So it appears that increase in concentration of the hydro- 

 bromic acid tends to carry the reduction below the condition 

 of the tetroxide ; but the highest degree of reduction reached 

 in these experiments corresponds to a mixture of one-sixth 

 tetroxide and five-sixths trioxide. 



Results somewhat similar were obtained with hydrobromic 

 acid made (first) by acting with bromine upon naphthalene and 

 purifying the gaseous acid by passing it through a column of 

 red phosphorus, and (secondly) by passing the vapor of bro- 

 mine with hydrogen over hot platinum somewhat after the 

 synthetic method of Harding,* and sending the product through 

 red phosphorus. In a single case in which the synthetic hydro- 

 bromic acid was used, the reduction, after three chargings of 



*Ber. Dtsch. ehem. Ges., xiv, 2085. 



