1 M. Berzelius o?i Vanadium. 



colour, and begins to emit fumes of nitric acid; it is then to 

 be suffei'ed to cool slowly. The pei-phosphate is slowly de- 

 posited in granular crystals of a fine lemon-yellow colour. 

 The mother-watei", become colourless, gives more crystals 

 when the nitric acid is evaporated. The perphosphate is 

 very slightly soluble in cold water, and may consequently be 

 fi'eed from nitric acid by washing. It contains water of cry- 

 stallization, which it loses at 212°; it then becomes of a straw 

 colour. Its solution in water is yellow. In the fire it is con- 

 verted into a mixture of phosphate and perphosphate. When 

 vanadic acid is dissolved in phosphoric acid, a syrupy mass is 

 obtained which does not crystallize. 



Perphosphate of' Vanadium and Soda. — When a little nitric 

 acid is added to a mixture of the phosphate and vanadate of 

 soda, it combines with the greater part of the soda, and the 

 solution yields, by evaporation, small lemon-coloured mam- 

 mellated crystals, which are more soluble in water than the 

 simple perphosphate. The solution of this salt, evaporated 

 to dryness, gives a yellow translucid varnish. 



Silicio-perpJiosphate of Vanadium. — This combination would 

 probably have been nnknown to me, if it had not been ob- 

 tained during the purification of vanadic acid obtained from 

 scoriae. In this case, small yellow crystalline scales are often 

 seen to form, which shine in the solution when it is stirred. 

 After having analysed these, I found that the salt might be 

 produced artificially. For this purpose a vanadate, a phosphate 

 and a silicate are to be mixed together, and nitric acid is to be 

 added in excess, which dissolves the whole ; it is afterwards 

 to be evaporated almost to dryness, and the residue is to be 

 mixed with water, the compound of the three acids then re- 

 mains undissolved, in the state of very light scales of a lemon 

 colour. These crystals are collected upon a filtre, and washed 

 with a little cold water, for they dissolve in considerable quan- 

 tity in hot water; they are then pressed and dried. This com- 

 pound redissolved in water reciystallizes in scales by spon- 

 taneous evaporation. This salt contains water of crystalliza- 

 tion, which it loses at a moderately high temperature, and be- 

 comes of a straw colour. It does not fuse at a red heat. It is 

 composed of 30 parts of phosphoric acid, 39 of vanadic acid, 

 19*5 of silica, and 1 1 '5 water. The oxygen of each of the three 

 last being 3, that of the phosphoric acid is 5. In order to 

 decompose it, it is treated with carbonate of ammonia, which 

 leaves the silica. Vanadic acid combines readily with silica, 

 and it appears that some other acids form analogous combina- 

 tions with vanadic acid and silica; for silicated vanadic acid 

 dissolves in sulphuric and muriatic acid, without the silica re- 



maininff 



