10 
PROFESSOR, ROSCOE’S RESEARCHES ON VANADIUM. 
Tube and reduced oxide after heating in hydrogen over three Bunsen’s lamps 
42-7689 grms. 
First heating in hydrogen gas in combustion-furnace 42-7678 grms. 
Second „ „ „ „ 42-7511 „ 
Third „ „ ,, ,, 42-7486 „ 
The atomic weight calculated from these numbers is Y=ol*485. 
Determination No. 4. — The acid used in this experiment was prepared by roasting, 
and afterwards completely oxidizing with nitric acid, pure ammonium vanadate which 
had been recrystallized four times, and had been prepared from acid obtained by the 
decomposition of the rectified oxychloride in water. The acid was free from phosphorus 
and silica, having been exposed, moistened with pure sulphuric acid*, for several days 
to the action of hydrofluoric-acid gas in a platinum vessel. Platinum boat and tube 
(constant weight) 25-2630 grms. 
„ „ „ second „ 30-3074 
„ „ „ third „ 30-3083 
„ „ „ fourth „ 30-3080 
Hence the weight of vanadium pentoxide taken =5-0450 grms. 
Boat, tube, and reduced oxide after first heating with hydrogen . 
,, „ „ „ second „ „ 29-4252 „ 
„ „ „ „ third „ „ 29-4244 „ 
„ „ „ „ fourth „ „ 29-4244 „ 
The atomic weight calculated from these numbers is V=51 - 353. 
On gently roasting the reduced oxide in a current of air, the constant weight 30-3074 
grms. was attained; this is within 0-0006 grm. of the original weight of boat, tube, and 
vanadic acid taken. 
The mean of these four determinations is 51-371 ; hence we may assume the atomic 
weight of vanadium, as obtained from the reduction of pentoxide to trioxide, to be 51-4 
as probably true to within ±0*07. 
Determination No. 1. 51-257, difference from mean —0-114 
„ No. 2. 51-391 „ „ „ +0-020 
„ No. 3. 51-485 „ „ „ +0-114 
„ No. 4. 51-353 „ „ „ -0-018 
Mean . . 
51-371 
Mean error +0-066 
is found to be 52-55 with a mean error 
of 0-12, whilst the subsequent estimations of Czudnowicz serve only as an approximate 
control of Berzelius’s number, giving a mean of 55-35 with a mean error of 2*33. 
* A special experiment proved that every trace of sulphuric acid is easily expelled from vanadium pentoxide on 
ignition. 
