drowning and Goodman — Estimation of Yanadium, 355 



Art. lit. — On the Application of Certain Organic Acids 

 to the Estimation of Vanadium ; by Philip E. Browning 

 and EiCHARD J. Goodman. 



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



In a former paper"^ by one of us a method for the determi- 

 nation of vanadium was described in which tartaric acid was 

 used to reduce vanadic acid to the condition of the tetroxide. 

 The method may be briefly outlined as follows : 



Measured and weighed portions of a solution of ammonium 

 vanadate, the standard of which had been determined by the 

 evaporation and ignition of definite portions, were treated with 

 tartaric acid in excess and boiled, wlien the appearance of the' 

 deep blue color indicated the reduction to the condition of the 

 tetroxide. After cooling, the solution was neutralized with 

 potassium bicarbonate and a moderate excess of that reagent 

 added. To the alkaline solution an excess of a standard solu- 

 tion of iodine was added and the whole allowed to stand about 

 one hour, when no further bleaching of the iodine was 

 noticed. t The excess of iodine was then destroyed with a 

 standard solution of arsenious oxide, starch was added, and the 

 blue color obtained with a few drops of the iodine solution. 

 The total amount of iodine used, less the amount equivalent to 

 the arsenious oxide solution used, is the amount necessary to 

 oxidize the vanadium from the condition of the tetroxide to 

 that of the pentoxide, from which, according to the following 

 equation, can be calculated the amount of vanadium present : 



The work to be described in this paper is in part an applica- 

 tion of the work described in the paper above mentioned to a 

 series of determinations of vanadium in the presence of 

 molybdenum and tungsten. The solution of vanadium used was 

 one of ammonium vanadate, and the standard was determined 

 by evaporating and igniting, in the presence of a drop of 

 nitric acid, measured and weighed portions, the mean of 

 closely agreeing results being taken as the standard. Our first 

 series of determinations was by the method previously 

 described, that being the natural starting point for the work 

 contemplated. The results follow in- the table : 



* Zeitschr. fiir anorgan. Chem. vii, 158. 



f These determinations are best made in small Erlenmeyer beakers, closed 

 with parafBn-coated cocks while standing with iodine. 



