W. A. Turner — Vanadium Determined by Cupferron. 339 



Art. XXIII. — The Determination of Vanadium by Cup- 

 ferron, C 9 B b N(OJ^B t ).NO; by W. A. Turner. 



[Contributions from the Kent Chemical Laboratory of Yale Univ. — cclxxvii.] 



The present paper gives the results of experiments begun 

 nearly two years ago on the determination of vanadium by 

 means of cupferron (the ammonium salt of nitrosophenyl- 

 hydroxylamine). At that time the actual determination of 

 vanadium by this means was not so much sought as its separa- 

 tion from the element uranium.* A large number of experi- 

 ments carried out for this purpose failed to reveal the proper 

 conditions for a successful separation of these two elements. 

 However something was learned of the reaction between 

 vanadium and cupferron and it is with this reaction and its 

 application to the estimation of vanadium that the present 

 paper deals. 



Vanadium in the form of its soluble vanadate in slightly 

 acid solution (hydrochloric or sulphuric) gives with cupferron a 

 mahogany red precipitate. This reaction is so delicate that it 

 may well be used as a qualitative test for a vanadate. If the 

 solution has a low concentration of vanadium a red coloration 

 instead of a precipitate is obtained. A solution containing 

 0*000004 gm. vanadium per cubic centimeter gives a distinct 

 coloration. Solutions of much lower concentration do not, in 

 my experience, give the test. 



A solution of ammonium metavanadate (prepared by pre- 

 cipitation from a solution of sodium vanadate by means of a 

 saturated solution of ammonium chloridef and then washing 

 until free from chlorides) was used for this work. The meta- 

 vanadate was dissolved in water by constant stirring and 

 gradual addition of concentrated hydrochloric acid. 



To obtain the vanadium content of this solution the volu- 

 metric method, which involves a reduction of the vanadate by 

 sulphurous acid and then oxidation by a measured amount of 

 standard KMn0 4 solution, was used. There was some incon- 

 venience in applying this method because of the fact that the 

 vanadium solution contained hydrochloric acid, which acted 

 upon the KMn0 4 , giving too high results. This difficulty was 

 overcome with some degree of success by evaporating the 

 weighed portions of vanadium solution with sulphuric acid to 

 remove the hydrochloric acid and then diluting and carrying 

 out the process above mentioned. 



* The use of cupferron for this purpose was suggested by Dr. W. M. 

 Thornton. While this work was in progress two papers by Kodeja have 

 appeared to which reference will later be made. 



•f Ann. Phys., xcviii, 54, 1831. 



Am. Jour. Sci.— Fourth Series, Vol. XLT, No. 244.— April, 1916. 

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