342 IF. A. Turner — Vanadium Determined hy Cupferron. 



sulphuric acid and 1*5 gms. of cupferron per liter. The solu- 

 tions and wash-liquid used should be cold ; that is, their tem- 

 perature should not exceed 20° C. If the temperature is 

 allowed to rise much above this the precipitate tends to decom- 

 pose and forms a gummy mass which clogs the pores of the 

 paper and makes filtering almost impossible. The precipitate 

 is ready to filter about as soon as formed and there should be 

 no delay in the filtration and washing. If the precipitate is 

 allowed to remain long on the filter it tends to crack and is 

 then more difficultly washed, while if the process is carried out 

 quickly and without interruption, it is readily filtered and 

 washed. 



By this process the following results were obtained : 



Table III. 



Exp. 



Gms. NH 4 VO s 



solution taken 



Gms. of V 2 5 

 found 



Gms. of V 2 B per 

 25 gms. of solution 

 found taken 



11 

 12 

 13 

 14 



25-4236 

 25-4193 

 25-3242 

 25-6816 



0-1686 

 0-1685 

 0-1673 

 0-1703 



0-1658 

 0-1657 

 0-1652 

 0-1658 



0-1655 

 0-1655 

 0-1655 

 0-1655 



From the above data it appears that the vanadium in vana- 

 dates can be very accurately estimated by means of the cup- 

 ferron reaction. Investigations are being made into the use 

 of this reagent for the separation of vanadium from other ele-. 

 ments, the results of which will appear at an early date. 



Recently the statement has been made by ftodeja* that 

 vanadium in the form of vanadates cannot be quantitatively 

 precipitated by cupferron, but that if the vanadate is first 

 reduced to the vanadyl condition a quantitative estimation of 

 the vanadium may then be made. Experiments made accord- 

 ing to the rather meager details given in the abstract of this 

 work failed to confirm this statement. 



Four portions of a solution of sodium vanadate, two of 

 which were precipitated without reduction and the other two 

 after reduction, gave the following results : 



* Abstract Journal of the Am. Chem. Soc, ix/2201, 2202, 1915. Anales 

 soe. Espan. fis. quiin., xii, 305-9, 379-82, 1914. 



