M. Berzeliiis on Va7iadium. 19 



at a boiling heat, nor even when it is subjected to their action, 

 without its being previously dried. They take half the acid 

 from the bivanadate. Sulphuric acid does not completely de- 

 compose vanadate of lead. It is requisite that the sulphate 

 of lead formed should be fused with bisulphate of potash, if it 

 be required to remove the last traces of vanadic acid. The 

 hydrosulphurets decompose vanadate of lead imperfectly, 

 leaving a subvanadate. 



Pervanadate of Uranium. — The neutral salt and the bisalt 

 are insoluble, and precipitate in the state, of a pale lemon- 

 yellow-coloured powder. 



Pervanadate of Copper. — It gives a yellow-coloured solu- 

 tion, and yields by evaporation a deep yellow amorphous mass. 

 The bisalt obtained by double decomposition, gradually de- 

 posits in the state of a yellow crystalline crust. 



Protovanadate of Mercuri/, obtained by double decom- 

 position, gives an orange-yellow-coloured solution, which de- 

 posits but a very little salt, becomes clear and retains its colour. 

 The bisalt, on the contrary, precipitates, and leaves the liquor 

 colourless ; the precipitate is of a very deep orange-yellow 

 colour. 



Va7iadate of Silver. — The neutral salt precipitates in the 

 state of a yellow mass, which becomes white in a few minutes. 

 It becomes yellow again when it is slightly heated, or when 

 it is left for twenty-four hours in the liquid in which it is pre- 

 cipitated. The bisalt forms a deep orange-coloured mass, 

 which does not become white, and dissolves sparingly in water 

 when washed. The vanadate is soluble in nitric acid, as well 

 as in ammonia largely diluted with water. The ammoniacal 

 solution is of a pale yellow colour, and gives by spontaneous 

 evaporation crystals of ammoniacal vanadate of ammonia. It 

 is precipitated by strong ammonia. The bixnnadate is very 

 soluble and crystallizes on cooling. 



Green Vanadates. — When the green oxide of vanadium is 

 combined with a small quantity of a base, a green compound 

 is formed. Such of these compounds as have an alkali for 

 their base are soluble in water ; those which have an earth or 

 metallic oxide are mostly insoluble. In the dry state they 

 appear black. It is difficult to say with certainty what these 

 green salts are : but it appears that they consist, either of 

 double salts composed of a vanadate and a vanadite, or of 

 hypovanadates, that is to say, of combinations formed of a 

 base with an acid, composed of two atoms of radical and five 

 atoms of oxygen, saturating a quantity of base which contains 

 two atoms of oxygen. The composition may very well be the 

 same on both these suppositions : but if tliat last mentioned 

 is the true one, the green salts should not be decomposed 



D 2 by 



