PROFESSOR ROSCOE’S RESEARCHES ON VANADIUM, 
323 
standing for a few hours the lower layer of liquid solidifies, forming an aggregate of colour-, 
less needle-shaped crystals. These crystals, which possess a strong alkaline reaction, are 
washed with small quantities of alcohol, then placed on a porous plate over sulphuric 
acid in vacuo, and after remaining for a short time they may be taken out for analysis. 
The following analytical results were obtained : — 
Water determination. — 0-8077 grm. of the crystals which first fuse in their water of 
crystallization lost on careful ignition in platinum 0-4882 grm. Ii 2 0; corresponding to 
60-44 per cent. 
Vanadium determination. — The residual anhydrous salt left in the crucible after the 
previous experiment, gave, on precipitation with lead acetate, a precipitate (dried at 
100° C.) weighing 0-7472 grm. ; 0-7245 grm. of this precipitate was dissolved in nitric 
acid, and the lead precipitated with slight excess of sulphuric acid, the usual precautions 
being taken. The filtrate from the lead sulphate yielded on evaporation 0-1515 grm. of 
finely crystallized V 2 O s . Consequently the whole lead precipitate contained 0*1565 grm. 
V 2 0 5 , corresponding to 19-34 per cent., or to 10-86 per cent, of vanadium, on the sodium 
salt taken. 
Sodium determination. — The liquid filtered off from the lead precipitate, and freed 
from excess of lead, left on evaporation and ignition 0-3440 grm. of Na 2 SQ 4 , corre- 
sponding to 0-1502 Na 2 0, or 13-8 per cent, of sodium in the salt. 
These numbers correspond to the formula 
Na 3 V0 4 -j- 16 H 2 O. 
Calculated. Found. 
]Sa 3 
. . / 69-0 
14-61 
13-80 per cent. 
Y . . 
. . 51-3 
10-86 
10-86 „ „ 
0 4 - . 
. . 64-0 
13-56 
16H 2 O 
. . 288-0 
60-97 
60-44 „ „ 
472-3 
100-00 
Sodium orthovanadate is an extremely unstable compound. Its aqueous solution 
slowly undergoes decomposition on standing at the ordinary temperature of the air out 
of contact with atmospheric carbonic acid, whilst at higher temperatures the same change 
takes place quickly. This decomposition consists in the formation of a new salt, sodium 
tetravanadate, the liquid becomes strongly alkaline, whilst caustic soda is liberated, 
according to the equation 
2(Na 3 V0 4 ) + H 2 0 = Na 4 V 2 0 7 + 2Na HO. 
This remarkable reaction was carefully investigated, as is seen in the sequel. 
I have not been successful in several attempts to prepare a tribasic sodium vanadate 
containing basic hydrogen. All the reactions which with the corresponding phosphate 
yield hydrogen-sodium salts give with the vanadate the tetrabasic compound above 
mentioned. The orthovanadates of most of the metals are insoluble compounds obtained 
