432 Vanadic Acid. 



is not very ductile or malleable, and can be easily reduced to 

 powder, like antimony, but is extremely difficult to melt. 



This metal lias not yet been applied to any useful purpose 

 in the arts, but it is probable, or, rather, almost certain, that 

 very small quantities of it in iron or other metals and alloys 

 have a considerable influence upon their qualities. Three or 

 four oxides of vanadium are known to exist, at least as labora- 

 tory products; one of them, vanadic acid, which will alone 

 occupy our attention here, is the state in which vanadium has 

 hitherto been found in nature. It is generally obtained as a 

 pale-chocolate-coloured powder, almost completely insoluble 

 in water, but soluble in alkalies, and fusible over a spirit-lamp. 

 It shows a beautiful phenomenon whilst cooling, to which I 

 have alluded in my work on Phosphorescence ; when melted 

 in a platinum crucible and allowed to cool slowly, it crystallizes, 

 and emits at the same time a reddish phosphorescent light, 

 during the whole time that the crystallization lasts. Several 

 other mineral substances, and boracic acid in particular, exhibit 

 the same curious emission of light when placed in similar cir- 

 cumstances. 



Another remarkable property of vanadic acid, which leads 

 us to imagine that this substance (so rare at the present day 

 that scarcely any laboratory in London possesses a specimen) 

 will be, some day or other, employed in the porcelain manu- 

 factories, is this : that when heated at the inner flame of the 

 blow-pipe with borax, or with the double phosphate of soda 

 and ammonia, it forms a beautiful green bead, a brilliant apple 

 green, which it would be desirable to see produced upon 

 porcelain. 



The metal vanadium has been very little investigated, be- 

 cause the sources of vanadic acid have been found hitherto to 

 be so extremely limited. Even the vanadate of lead discovered 

 by Del Rio, which contains about 23 per cent., and similar 

 minerals from Rhenish Bavaria and South America, giving 

 46 to 49 per cent, of vanadic acid (the Scotch specimens give 

 1 5 to 23 per cent.), are very rare ; and the same remark 

 applies to a vanadate of copper found occasionally in Transyl- 

 vania and Thuringia, which contains 36 to 39 per cent, of the 

 substance in question. 



Vanadic acid has, however, been met with as an accidental 

 constituent of several mineral substances,*more or less plentiful, 

 particularly in hydrated oxides of iron, in pitchblend (oxide 

 of ur;i nium), etc. We shall see, presently, the names of all 

 those substances from wliich it has, up to the present day, 

 been extracted. 



In 1859, a young French chemist, M. Beauvallet, announced 

 the existence of small quantities of vanadic acid in the clay 



