M. Berzelius 0// Vanadium. 11 



maining undissolved. There is no other method of separating 

 them, but that of treating them simultaneously with fluoric and 

 sulphuric acid. The alkalies dissolve the silicated vanadic 

 acid, and during evaporation the liquid frequently becomes a 

 gelatinous mass. The silica, separated from the vanadic acid 

 by an alkaline carbonate, is in the same state of solubility as 

 that precipitated by water from fluosilicic acid. It contains 

 however some vanadic acid, which can be separated only by 

 an alkaline hydrosulphuret. 



Perarseniate of Vanadium. — The protoarseniate treated 

 with nitric acid gives a salt of a lemon-yellow colour, which 

 perfectly resembles the phosphate. 



The oxalic, tartaric and citric acids decompose vanadic 

 acid, when they are in excess; they form at first a yellow so- 

 lution, which in a short time passes to green and blue. When 

 however these acids are not in excess, their union with vanadic 

 acid may be permanent. Thus after having oxidized oxalate 

 of vanadium by nitric aciil, and separated the latter by eva- 

 poration, the mass being treated with water yields a solution 

 of a yellowish orange colour, which leaves by evaporation per- 

 oxalate of vanadium in the form of a reddish yellow extract. 



Acetic acid, even when concentrated, does not dissolve a 

 particle of vanadic acid ; formic acid dissolves a litde, but the 

 solution is colourless ; by evaporation a yellowish translucid 

 mass is obtained, which is performiate of vanadium. 



The Vanadites* are saline combinations of the oxide of 

 vanadium with substances which are more electropositive than 

 itself. I have studied them but little. They are usually of 

 a brown colour; when moist, they oxidize rapidly in the air, 

 and are converted into vanadates. Sulphuretted hydroo-en con- 

 verts them into sulphovanadites. Acids change their colour 

 to blue, occasioning the formation of double vanadites. Infu- 

 sion of galls colours them of so deep a blue as to appear black. 



Vanaditc of Potash. — This salt is easily obtained by mixino- 

 a hot solution of sulphate or chloride of vanadium with a 

 slight excess of caustic potash, and allowing the brown liquor 

 to cool slowly in a full and well closed vessel. The vanadite 

 crystallizes gradually in brownish brilliant scales, and the solu- 

 tion becomes gradually paler, until it is eventually transparent 

 and very slightly coloured. The crystals are to be separated 

 from the mother-water, washed with pure alcohol, and dried, 

 with [)ressure, between folds of filtering paper. Dry vanadite 

 of potash is permanent in the air. 1 left some for two months 



The author's nomenclature is scarcely admissible. Does an oxide 

 become an acid by combining with another oxide? — Edit. 



C 2 in 



