hillebrand.] VANADIUM (CHROMIUM) AND MOLYBDENUM. N. r > 
solution will show some coloration, and addition of an acid precipitates 
brown vanadium sulphide, which can be collected, ignited, and further 
tested if desired. 
APPLICATION OF THE METHOD IN PRESENCE OF RELATIVELY MUCB CHROMIUM. 
The application of the method in its foregoing simplest form is 
subject to one limitation — the chromium must not be present above ;i 
certain moderate amount. This limitation is due to the considerable 
amount of permanganate then required to produce a clear transition 
tint when titrating in a hot solution, as is advisable with vanadium. 
In a cold solution of chromic sulphate much less permanganate is 
needed to produce the peculiar blackish tint without a shade of green, 
which affords a sure indication of excess of permanganate, but in a 
hot and especially a boiling solution the oxidation of the chromium 
itself takes place so rapidly that a very large excess of the reagent 
may be added before a pronounced end reaction is obtained. Never- 
theless, quite satisfactory determinations of as little as one or two 
milligrams of vanadium pentoxide can be made in presence of as much 
as 30 milligrams of chromic oxide. To accomplish this it is only 
necessary to apply a simple correction obtained by adding permanga- 
nate to a like bulk of equally hot chromic sulphate solution containing 
approximately the same amount of chromium. 
Ridsdale 1 titrated the cold solution to avoid oxidation of chromium, 
and obtained accurate results, but in the writer's experience the end 
reaction is then uncertain. 
i Jour. Chcm. Soc, Vol. VII, p. 73, 1888. 
