Gooch and Edgar — Redaction of Vanadlc Acid. 237 



acid by zinc. The details of experiments made in the reduction 

 flask with zinc and hydrochloric acid are given in A; the record 

 of experiments also made in the reduction flask with zinc and 

 sulphuric acid is given in B ; and C contains the data of 

 experiments made with the Jones reductor,* in which a column 

 of amalgamated zinc 40 cm long and 2 om in diameter was used. 

 In all these experiments the titration was effected directly in 

 air by nearly N/10 potassium permanganate. The V 2 5 is 

 calculated upon the hypothesis that the redaction goes to the 

 condition of V 2 2 . 



From the results of Table II it is evident that in no case does 

 the condition of oxidation of the product of the reduction of 

 vanadic acid by zinc and hydrochloric acid in the flask, by 

 zinc and sulphuric acid in the flask, or by amalgamated 

 zinc in the reductor, correspond exactly to V 2 2 when 

 titration is made in air. A series of experiments was made, 

 therefore, in which care was taken to protect the reduced 

 solution from the action of air until the highest degree of 

 oxidation is past and registered, by an adaptation of a method 

 used by Randallf for the accurate titration of molybdic 

 acid similarly reduced by the column of amalgamated zinc.;j; 

 According to this procedure, the receiver attached to the zinc 

 column was charged with a solution of ferric alum, gentle suc- 

 tion was applied to the receiver, and in succession were passed 

 through the column of amalgamated zinc, hot water (100 cm3 ), 

 2*5 per cent sulphuric acid (100 cm3 ), the solution of vanadic 

 acid in 2 - 5 per cent sulphuric acid (125 cm3 ), and finally hot water 

 (200 cm3 ). To the receiver was added syrupy phosphoric acid 

 (4 cm3 ), to decolorize the solution, and the titration was made in the 

 hot solution in the usual manner with potassium permanganate. 

 Table III contains the results of these experiments, corrected 

 for the action of the zinc column upon the reagents without 

 the vanadic acid. 



The results of Table III show plainly that the action of the 

 column of amalgamated zinc carries the reduction easily and 

 rapidly to the condition of V 2 2 , and that by anticipating the 

 oxidizing action of the air by means of a ferric salt in the 

 receiver the solution is made less sensitive to the action of the 

 air, while the highest degree of reduction is registered by the 

 ferrous salt formed. A comparison of these results with those 

 of Table II shows unmistakably that a solution containing 

 vanadium in the condition of V 2 2 cannot be exposed to air, 

 even momentarily, without undergoing oxidation. 



* " The Chemical Analysis of Iron," Blair, 6th ed., 225. 



f This Journal, xxiv, 313. 



\ We are indebted to Professor Henry Fay for the information that this 

 mode of treating reduced molybdic oxide was first worked out many years 

 ago by Dr. C. B. Dudley, though never published. 



