PROFESSOR ROSCOE’S RESEARCHES ON VANADIUM. 
321 
Weight of tribro- 
Vanadium 
Loss of 
Percentages 
inide taken. 
pentoxide 
bromine. 
-A. 
found. 
of vanadium. of bromine. 
(1) 
0-8004 
0-2630 
0-6500 
18-46 
81-21 
(2) 
0-3462 
0-1160 
0-2790 
18-80 
80-58 
( 3 ) 
0-5960 
0-1965 
0-4815 
18-52 
80-85 
Hence we have : — 
Found. 
Calculated. 
*\ 
r~ 
— \ 
(!)• 
(2). (3). 
Mean. 
V = 
. . 51-3 
17-6 
18-46 
18-80 18-52 
18-59 
Br 3 = 
. . 240-0 
82-4 
81-21 
80-58 80-78 
80-86 
291-3 
100-0 
99-67 
99-38 99-30 
99-45 
Experiments made with the bromine employed, which had been rectified over potas- 
sium bromide, and was carefully tested for chlorine and iodine and showed to be pure, 
proved that a similar excess of weight occurred on precipitation with nitrate of silver. 
In one experiment the percentage of bromine thus found was 100-96, and in a second 
experiment 101-41. It will also be seen that the bromine determinations of the oxybro- 
mides are similarly all too high from the same cause. 
III. VANADIUM AND IODINE. 
When the vapour of iodine is passed over the red-hot nitride of vanadium contained 
in a tube no action whatever takes place, the nitride after the operation remaining per- 
fectly unchanged. Vanadium trioxide is likewise unacted upon by iodine at all tempe- 
ratures. 
IV. METALLIC VANADATES. 
In the first Part of these researches* I pointed out (1) that the vanadates analyzed by 
Berzelius, prepared by boiling vanadic acid with the alkaline hydroxides and by double 
decomposition, must be considered as meta- or monobasic vanadates, (2) that the so-called 
bi-vanadates analyzed by Von Hauer f, and prepared by acting on the meta vanadates 
with acids are anhydro-salts, and (3) that the naturally occurring vanadates are tribasic 
salts, and that sodium ortho-vanadate is formed when one molecule of vanadium pentoxide 
is fused with three molecules of carbonate of soda, three molecules of carbon dioxide being 
expelled. I have now to describe the preparation and properties of some characteristic 
members of these three classes of vanadates, as well as those of a fourth new class, viz. 
the tetrabasic or pyro-vanadates. 
Determination of vanadium in the soluble vanadates . — The separation of vanadic acid 
from the metals of the alkalies by means of chloride of ammonium, as proposed by Von 
Hauer, is apt to give too low results, both as regards the vanadium and the alkali. It 
* Philosophical Transactions, 1868 (Bakerian Lecture), 
t Journ. Prac. Chern. Bd. lxix. p. 388, 1856. 
