Prof. Roscoe on Vanadium. 65 



3. Vanadium Oxydibromide, or Vanadyl Dibromide,V OH$r 2 , molec. 

 wt. =227*3. — This is a solid substance, of a yellowish-brown colour, 

 obtained by the sudden decomposition of the foregoing compound 

 at temperatures above 100°, or by its slow decomposition at the 

 ordinary temperature. 



The oxydibromide is very deliquescent, dissolving in water, with 

 formation of a blue solution of a vanadious salt. "When heated in the 

 air it loses all its bromine, and is converted into V 2 O.. 



Analysis gave : — 



V = 51-3 



Br 2 =160-0 



O ,. = 160 



Calculated. 



Mean of several analyse, 



22-57 



22-45 



70-39 



70-93 



7-104 







227-3 100-00 



III. Vanadium and Iodine. 



Iodine-vapour does not attack either the trioxide or the nitride 

 at a red heat ; both these substances remain unchanged, and no trace 

 of vanadium can be detected in the iodine which has passed over 

 them. 



IV. The Metallic Vanadates. 



In the first part of these Researches (Phil. Trans. 1868) it was 

 pointed out (1) that the salts analyzed by Berzelius must be consi- 

 dered as meta- or monobasic vanadates, (2) that the so-called bi va- 

 nadates analyzed by Von Hauer are anhydro-saits, and (3) that the 

 ortho- or tribasic vanadates contain 3 atoms of monad metal, the 

 sodium salt being formed artificially by fusing 1 molecule of vanadium 

 pentoxide with 3 molecules of carbonate of soda, when 3 molecules 

 of carbon dioxide are expelled, whilst the orthosalts occur native in 

 many minerals. The present communication contains a description 

 of these classes of salts, as well as of a new class of salts, the tetra- 

 basic or pyro-vanadates. 

 Sodium Vanadates. 



^ 1 . Ortho- or Tri-Sodium Vanadate, Na 3 V0 4 + 1 6H 2 2 .— When a 

 mixture of 3 molecules of Na a C0 3 and 1 molecule of V 2 5 is fused 

 until no further evolution of C0 2 is observed, a tribasic vanadate 

 remains as a white crystalline mass. This mass dissolves easily in 

 water, and on addition of absolute alcohol to the solution two layers 

 of liquid are formed ; the lower one solidifies after a time, forming an 

 aggregation of needle-shaped crystals, which possess a strongly alka- 

 line reaction. These having been washed with alcohol, and dried on 

 a porous plate over sulphuric acid in vacuo, were analyzed with the 

 following results : — 



Phil Mag. S. 4. Vol. 40. No. 2G i. My 1870. F 



