M. Berzelius on Vanadium. 13 



isomeric phaenomenon, analogous to the changes which the 

 phosphates undergo in the fire. When a solution of bivana- 

 date of ammonia is saturated with ammonia and the solution 

 suffered to evaporate spontaneously, it retains its colour and 

 yields a yellow salt; but by heating part of the same solution 

 it becomes colourless and gives a white salt. When bivana- 

 date of potash is saturated with potash, the solution preserves 

 its colour for an hour or two, and it then begins to disappear. 

 If a solution of chloride of barium be precipitated by a colour- 

 less solution of vanadate of ammonia, the mixture becomes 

 yellow, and a yellow precipitate is formed in a fluid of the 

 same colour. At the expiration of twenty-four hours, the salt 

 and mother-water become both colourless; but they lose their 

 colour instantly if heated to ebullition. This last experiment 

 proves that the disappearance of the colour does not depend 

 upon the slow formation of a compound, for substances al- 

 ready combined and neutral undei'go it. Weak bases, such 

 as the earths properly so called, and the greater part of the 

 metallic oxides, give coloured salts, which do not lose their 

 colour by the action of heat. 



The acids, such as the muriatic, develop a red coloin* in 

 the neutral vanadates, which disappears in an hour or two, 

 so that the solution becomes colourless. If it be then evapo- 

 rated at the temperature of 104° Fahrenheit, it gradually de- 

 posits a mass of a red-brown colour, which is a supervana- 

 date, provided that the excess of acid is not such as to form 

 a compound of the two acids. It dissolves much better in 

 water than in pure acid ; the solution is red, and gives, by 

 evaporation, a red polished varnish, which rarely has any cry- 

 stalline appearance. The vanadates do not derive any pecu- 

 liar taste from their acid. They are insoluble in alcohol. 

 Infusion of galls gives them so deep a blue, that the liquid 

 perfectly resembles common ink. 



Vanadate of Potash. — It is very soluble in water; the so- 

 lution, of a syrupy consistence, becomes by spontaneous eva- 

 poration a saline mass, which eventually is opake, and of a 

 dirty-white colour. Like most salts which contain vanadium, 

 it dissolves very slowly in cold water; part of the salt remains 

 a long time in the water, and has the appearance of a white 

 earth. In boiling water, the solution is more rapid. The 

 salt is very fusible in the fire. I cannot positively assert that 

 this salt can exist in a coloured state when it is solid; I have 

 obtained some which was coloured ; but the colour may be 

 attributed to the presence of a very small quantity of bivana- 

 date. When the colourless solution has acquired a certain 

 degree of concentration, it begins to become yellow, and finishes 

 by becoming a pale yellow mass. This pha-nomcnon occurs 



only 



