Gooch and Stookey — Reduction of Yanadic Acid, etc. 369 



Art. XXX YI. — The Reduction of Yanadic Acidby the Action 

 of Hydrochloric Acid; by F. A. Gooch and L. B. Stookey. 



[Contributions from the Kent Chemical Laboratory of Yale University— CXII.] 



BuNSEN^ and MoHRf have proposed to estimate vanadic 

 acid by the action of concentrated aqueous hydrochloric acid, 

 thus reducing it from the condition of oxidation represented 

 by the pentoxide to that of the tetroxide, in accordance with 

 the equation 



and determining iodometrically the chlorine evolved. 



In an attempt by Czudnowicz;}: to make use of this reaction 

 by collecting in standard arsenious acid the chlorine evolved 

 from the boiling mixture of hydrochloric acid and vanadic acid, 

 and titrating the excess of the arsenious acid by iodine, 

 accordant results were not obtained. On the other hand, 

 Gibbs§ was able to determine with a fair degree of accuracy 

 the sujall amounts of vanadium pentoxide found in the vana- 

 dio-tungstates and other complex combinations, by boiling 

 with strong hydrochloric acid, collecting in potassium iodide 

 the chlorine evolved, titrating the freed iodine with sodium 

 thiosulphate, and calculating from the amount of iodine thus 

 found the vanadium pentoxide corresponding to a change of 

 condition from Yfi^ to Yfi^. 



Milch] was unable to substantiate the work of Gibbs, and, 

 obtaining in four experiments, upon approximately 0*2 grm., 

 0*5 grm., and 1*0 grm. of vanadium pentoxide, amounts of 

 chlorine varying with the quantity of material handled and 

 never exceeding one-fourth of the amount demanded by theory, 

 was led to suppose that the degree of reduction was not con- 

 stant, being larger in proportion as the quantity of pentoxide 

 used was smaller. Milch concluded that while accordant 

 results might be obtained by w^orking with approximately 

 similar amounts of material, the process afforded no ground for 

 the calculation of the actual amount of pentoxide present. 



RosenheimTf also tested the process, working with pure van- 

 adates and pure vanadium pentoxide. Concentrated hydro- 

 chloric acid, of sp. gr. 1*19, was employed and care was taken 

 to dry the distillation flask before introducing the materials, 

 because even slight dilution of the acid lessened the evolution 



* Ann. Chem. (Liebig), xcvi, 265. f Titrirmethode v. Aiifl., 314. 



:{;Ann. Phys., cxx, 17. § Proc. Amer. Acad., x, 250. 



IJInaug. Dissert., Berlin, 1887, 10. 

 ■[[Inang. Dissert., Berlin, 1888; Ann. Chem. (Liebig), ccli, 197. 



