326 M. Berzelius oti Vanadium. 



losing oxygen, if it he preserved from the influence of com- 

 bustible bodies. When fused it crystallizes on cooling, and 

 then exhibits a phfenomenon, which merits observation. It 

 solidifies at a heat which is invisible in ilaylight ; but the mo- 

 ment that solidification commences, a luminous circle extends 

 from the periphery to the centre, where, owing to latent heat 

 becoming free, the mass remains red hot as long as the cry- 

 stallization continues. The acid contracts much on solidify- 

 ing, and is readily detached from the crucible : it is then of 

 a yellowish red colour, and formed entirely of a mass of inter- 

 laced crystals. Cavities frequently occur containing small and 

 perfectly regular crystals, the form and size of which may be 

 determined, when opportunity offers of repeating the experi- 

 ment with about 300 grains. Fused vanadic acid is translu- 

 cent at the edges, and has a yellowish colour. When it is 

 impure, or when it has been in part reduced to the state of 

 oxide, it does not crystaUize ; but at the moment of its solidi- 

 fication, excrescences are produced in the form of cauliflowers, 

 and the solidified mass is blackish. If the acid contains a 

 very small quantity of oxide, it crystallizes, but afterwards 

 assumes a violet colour. Vanadic acid is not a conductor of 

 electricity. It is slightly soluble in water, to which it imparts 

 a bright yellow colour. If the pulverulent acid be put into 

 water and well stirred, it mixes with it so as to produce a 

 turbid fluid of a yellow colour, which does not become clear 

 for several days : 1000 parts of boiling water scarcely dissolve 

 one part of vanadic acid, but the cooled solution remains trans- 

 parent. The acid is deposited by evaporation in the form 

 of red concentric rings. The last portion gives yellowish 

 microscopic crystals, but they become green when heated. 

 It is a compound of vanadic oxide and acid, produced appa- 

 rently by the influence of dust floating in the air; a phaeno- 

 menon similar to the partial reduction of a solution of oxyman- 

 ganic acid, which is attributed to this cause. It is in general 

 impossible to crystallize vanadic acid in the humid way, and 

 it is equally so to extract it in an isolated state from a solution, 

 because it combines equally with acids and bases. It is easily 

 reduced to the state of oxide, especially under the influence 

 of an acid; red nitric acid, sulphurous acid, several vegetable 

 acids, especially the oxalic and tartaric, alcohol, sugar, &c. 

 effect this reduction at a moderate temperature. Muriatic 

 acid dissolves and becomes of an orange colour; but soon 

 afterwards chlorine is disengaged, and the solution then pos- 

 sesses the property of dissolving gold and platina. Vanadic 

 acid, fused on charcoal by the blowpipe, leaves a coherent 

 mass, of the colour of plumbago, which is the suboxide of 



vanadium: 



