M. Berzelius on Vanadium. 327 



vanadium : with the phosphate of ammonia and soda it gives 

 a fine green colour to glass, which appears brown while it is 

 hot. The blue colour of the salts of vanadium cannot be pro- 

 duced, even on adding metallic tin to the flux. With borax 

 it also gives a green glass. In this reaction vanadium resem- 

 bles chromium, but the green colour produced by the former 

 may be changed to yellow by the oxidating flame, which does 

 not happen with chromium. This change is easily effected, 

 especially with the glass of borax. With carbonate of soda it 

 is not reduced to the metallic state. Vanadic acid is composed 

 of 74-0+4-9 parts of vanadium and 25-9551 of oxygen, that is 

 to say, S50533 of the latter, and 100 of the former; conse- 

 quently the metal is combined with three times as much oxy- 

 gen as in the suboxide. Its saturating capacity is equal to 

 one third of the quantity of oxygen which it contains, that is 

 to say, 8-6517. 



4thly, Intermediate Oxides of Vanadium. — We have seen 

 that the suboxide and oxide of vanadium, when exposed to 

 the influence of the air, acquire the property of colouring 

 water green. The vanadic oxide and acid combine together 

 in different proportions ; two of these compounds have the 

 property of forming with water a solution of a fine green co- 

 lour. Other compounds are purple and orange coloured. 

 They pass, by the influence of the air, from one degree of 

 oxidation to a higher one. 



a. Purple Oxide. — If vanadic acid be kept for twenty-four 

 hours in a badly corked bottle, and water be then added to 

 it, it becomes of a green colour. The mass is then to be poured 

 upon a filter, and when the green liquor is filtered a fresh 

 portion of water is added; the fluid which then filters is much 

 deeper coloured and brownish; a fresh quantity of water 

 assumes a fine purple colour, and when the washings have 

 been thus continued for some time, the water passes through 

 colourless. The residue exposed for some time to the air 

 acquires the property of reproducing the phaenomena which 

 have been described, and eventually a new purple liquid is ob- 

 tained. This solution holds but little matter in solution; it 

 may be preserved in a full bottle hermetically sealed, but on 

 exposure to the air it soon becomes green and afterwards yel- 

 low. The vanadic acid appears to be combined with the 

 greatest quantity of oxide of vanadium that it is capable of 

 rendering soluble. It may be called a subvanadate of vana- 

 dium. 



b. Vatiadate of Vanadium. — If hydrate of vanadium be 

 allowed to dry in the air, and then digested in a very small 



(juantity 



