324 
PEOEESSOE EOSCOE’S EESEAECHES ON VANADIUM. 
by precipitating neutral solutions of the soluble metallic salts with a solution of ortho' 
vanadate of sodium. The reactions of the more important metals are as follows : — 
1. Ferric salt . . 
2. Ferrous salt 
3. Manganous salt 
4. Zinc salt . . 
5. Cobalt salt . . 
6. Nickel salt . 
7. Aluminium salt 
8. Copper salt . . 
9. Mercuric salt . 
Reactions of the Orthovanadates. 
. Gelatinous precipitate of a light brownish-yellow colour, soluble 
in hydrochloric, insoluble in acetic acid. 
. Dark grey precipitate. 
. Brownish-yellow crystalline precipitate. 
. White gelatinous precipitate. 
. Brown-grey gelatinous precipitate. 
. Canary-yellow crystalline precipitate. 
. Bright yellow gelatinous precipitate, soluble in excess of both 
reagents ; on boiling a white precipitate is again thrown down. 
. Apple-green coloured precipitate. 
. Orange-yellow precipitate. 
The reaction which serves best to distinguish the ortho- from the metavanadates is 
that of the corresponding copper salts. Orthovanadate of copper possesses a bright 
apple-green colour, whilst the metavanadate falls down a light yellow crystalline powder. 
2. Tetrasodium Vanadate , or Pyrovanadate, Na 4 V 2 0 7 +18H 2 0. — This salt crystallizes 
in beautiful six-sided tables. It is easily soluble in water, insoluble in alcohol, and is 
precipitated from aqueous solutions by the latter liquid in the form of white scales of a 
pearly lustre. The pyro vanadate can be readily obtained by fusing one molecule of 
vanadium pentoxide (V 2 0 5 ) with two molecules of sodium carbonate (Na 2 C0 3 ), dis- 
solving and crystallizing. It can also be obtained by the decomposition of the ortho- 
vanadate in aqueous solutions. As long as the tetrabasic salt contains free alkali, from 
the decomposition of the orthovanadate, the precipitate with alcohol forms oily drops, 
which only solidify after some time, whilst the pure salt is at once thrown down in the 
form of silky scales. If the fusion of vanadium pentoxide with three molecules of car- 
bonate of soda be not completed at a very high temperature, the carbonate is not fully 
decomposed, and the fused mass when dissolved in water crystallizes at once in six-sided 
tables, or, if the solution be very concentrated, in nodular groups of needle-shaped 
crystals. The tetrabasic salt is more easily fusible than the tribasic salt, and on cooling 
from fusion it also forms a crystalline mass. 
Decomposition of Tribasic into Tetrabasic Vanadates by boiling the agueous solution . — 
That a decomposition of the above nature takes place is seen by the analyses of the dif- 
ferent samples of 4 basic sodium salt which follow, not one of which was prepared by 
fusing two molecules of the carbonate with only one of vanadic acid, but by repeatedly 
recrystallizing the tribasic salt. The decomposition is not brought about by atmospheric 
carbonic acid ; for in the following experiments the solution of the salts and the filtration 
of their solutions were effected in an apparatus from which all access of carbonic acid 
