48 
CONTRIBUTIONS TO CHEMISTRY AND MINERALOGY. 
fused with a little sodium carbonate, leached with water, and filtered 
into a small graduated flask. After colorimetric determination of the 
chromium, sulphuric acid was added, both chromium and vanadium 
were reduced by sulphur dioxide gas, and the titration carried out as 
described. 
Table III. — Test determinations of vanadium added to rocks and ores in presence of 
chromium. 
Vanadium 
pentoxide. 
No. 
Chromic oxide. 
Vanadium 
pentoxide. 
Found. 
Error. 
Mgs. 
Mas 
Mgs. 
Mg. 
a 22 
7 
6.76 
6.81 
6.48 
6.43 
6.37 
+0.05 
— .28 
— .33 ' 
— .37 
a 23 
3 
3 
3.08 
3.13 
3.03 
3.08 
+ .08 
+ .13 
+ .03 
+ .08 
&24 
1.6 
1.87 
1.86 
1.97 
2.07 
1.86 
— .01 
+ .10 
+ .20 
— .01 
a Five grams iron ore. 
&T\ro grams silicate. 
These and other experiments show that by taking not over 5 grams 
of ore or rock, vanadium, if present to the extent of 0.01 or 0.02 per 
cent, can be readily estimated by exercising reasonable care in all 
the operations. Absolute confirmation of its presence can be easily 
obtained by evaporating and igniting the solution to remove excess of 
sulphuric acid, taking up with a few drops of dilute nitric acid, and 
adding to the solution in a test tube a drop or two of hydrogen per- 
oxide. In this way positive or negative assurance as to the presence 
of vanadium is given when the result of titration alone might be 
uncertain. Addition of ether at the same time affords a simultaneous 
test for chromium by its blue color, and this might, perhaps, be made 
use of, if necessary, to remove all or the greater part of the chromium 
prior to titration of the vanadium, since the oxidation product of the 
latter does not dissolve in the ether. 
It is even possible that the dark-brown color produced by hydrogen 
peroxide might be utilized for an exact colorimetric method for esti- 
mating vanadium. 
