hillebrand.] VOLUMETUIC ESTIMATION OF VANADIUM. 
47 
Table II. — Application of degree of correction for larger amounts of chromium, obtained 
by adding potassium permanganate to an equal bulk of solution containing a like 
amount of chromic sulphate. 
No. 
Chromic 
oxide. 
Vanadium 
pentoxide. 
Vanadium pentoxide found. 
Error. 
Volume 
Of 
solution. 
Uncorrected. 
Corrected. 
Mgs. 
Mgs. 
Mys. 
Mgs. 
?,!,,. 
cc. 
16 
20 
0. 94 
1.59 
0.99 
+0.05 
50-100 
17 
20 
1.87 
2. (59 
2. 39 
2.59 
2.09 
1.79 
1. 99 
+ .22 
— .08 
+ -12 
50-100 
18 
20 
18.74 
19.4 
19.3 
19.3 
• 18.73 
18.63 
18.63 
— .01 
— .11 
— .11 
50-100 
19 
30 
1.87 
2.99 
2.79 
2.79 
2.69 
2.69 
2.14 
1.94 
1.94 
1.84 
1.84 
+ .27 
+ .07 
+ .07 
— .03 
— .03 
a 100 
20 
30 
1.87 
2.69 
2.89 
2.89 
2.79 
1.79 
2.09 
2.09 
1.89 
— .08 
-f .22 
+ .22 
+ -12 
200 
21 
62 
46.85 
48.60 
47.60 
+ .75 
200 
a About. 
In spite of the tact that the correction in most of the trials of this 
last table represents a large proportion of the permanganate used, the 
results must be considered satisfactory in view of the small amount of 
vanadium present, and they show that the method in competent hands 
after a little experience affords trustworthy figures. 
Testing the Method on Rocks and Ores. 
The following table shows its availability for rocks and ores. Known 
amounts of both chromium and vanadium were added to an iron ore 
and to a silicate, both free from arsenic, which were then fused with 
sodium carbonate and nitrate and further treated as follows: After 
extracting with water and reducing manganese by alcohol, the silica 
and alumina were mostly removed by nearly neutralizing with nitric 
acid and evaporating to near dryness. The washed precipitate was 
ignited and treated with hydrofluoric and sulphuric acids, the residue 
fused with sodium carbonate, since it frequently contains a little 
chromium, and again nearly neutralized, etc. To the combined and 
slightly alkaline filtrates was added mercurous nitrate, the precipitate of 
phosphate, vanadate, chromate, and carbonate was ignited in platinum, 
