322 Mr Johnston on Vanadium. 



sparingly in solutions of caustic and carbonate of ammonia, 

 with a rose red* colour; the oxide of vanadium dissolves easily 

 in ammonia, giving a translucent dark brown or olive solution, 

 from which it cannot be precipitated by alcalies, as oxide of 

 chromium can. 



3. Both acids are red and fuse into a red liquid ; but while 

 the chromic is changed at a higher temperature into the in- 

 fusible oxide, the vanadic, according to Sefstidm, parts with 

 a small portion of its oxygen, and crystallizes on cooling, as 

 already stated. 



4. The chromic acid never loses its colour, neither by heat- 

 ing nor by combinations with the bases. A solution of the 

 vanadic occasionally loses its colour by heating; and forms, 

 with excess of base, colourless salts similar to the vanadiate 

 of ammonia, mentioned above. The presence of vanadic acid 

 may be at once detected in any of these colourless salts or so- 

 lutions by a drop of nitric acid, which reddens the salt and 

 makes the solution yellow. The crystallized acid or fo'-vana- 

 diates are not to be distinguished in colour from the bi-chxo- 

 mates. 



5. Both metals give volatile chlorides, but that of vanadium, 

 as already stated by Berzelius, (An. de Chim. xlv. p. 332,) is 

 not always coloured. If a mixture of a chromate and a chlo- 

 ride be heated with sulphuric acid in a tube sealed at the one 

 end, a beautiful red gas is given off, which condenses if the 

 finger be kept on the mouth of the tube into a beautiful red 

 liquid. A similar mixture of avanadiate with a chloride heat- 

 ed in the same way gives a colourless gas. 



6. Solutions of the vanadiates give, with the metallic salts 

 in general, precipitates resembling those given by the chro- 

 mates. The salts of lead and mercury form the most striking 

 exceptions. Newly precipitated chromate of lead is of a bright 

 yellow, which it retains when dry, forming the beautiful and 

 well known pigment. The vanadiate of lead, at first bright 

 yellow, is bleached by the action of light, and becomes occa- 

 sionally pure white. Were it plentiful, therefore, it could 

 never take the place of the chromate in the arts. 



* Gmelin's Handbuch, i. p. 815. 



