M. Berzelius on Vanadium. 325 



pure oxide of vanadium in the dry way, 9-5 parts of suboxide 

 of vanadium are to be mixed with 11-5 parts of vanadic acid, 

 and the mixture is to be heated to whiteness, in an atmosphere 

 of carbonic acid gas. In the moist way, it may be obtained 

 by precipitating a blue vanadic salt, previously treated by 

 sulphuretted hydrogen, sugar or alcohol, in order to destroy 

 all the vanadic acid which it may contain. This solution is to 

 be precipitated by carbonate of soda, added slightly in excess. 

 A grayish white precipitate is formed, which is collected on a 

 filter and washed, without the contact of the air. It is to be 

 pressed between folds of filtering paper and dried i7i vacuo. 

 It is gray, inclining to brown : it is hydrated oxide of vana- 

 dium, sometimes containing traces of carbonic acid. When 

 heated to redness in vacuo, it yields water and leaves the oxide 

 in the state of a black powder, which does not blue litmus 

 paper that has been previously reddened. Oxide of vanadium 

 is not fusible at the temperature at which glass softens. It is 

 insoluble in water, but if it remains long in it the water becomes 

 gradually green, in consequence of increased oxidation. The 

 hydrate rapidly oxidizes in the air, and becomes first brown 

 and afterwards green ; when dried it is black : it will be again 

 noticed. Oxide of vanadium which has been heated, dissolves 

 slowly but completely in acids; the solution is blue, and the 

 oxide acts as a base; but it combines with bases and foi'ms 

 salts, which may be called vanadites. The alkaline carbonates 

 dissolve it; the solution, which is of a deep brown, contains a 

 vanadate and a bicarbonate ; the bicarbonates also dissolve it, 

 and assume a blue colour : it appears that this solution con- 

 tains neutral double carbonate of vanadium and alkali. Oxide 

 of vanadium is composed of 8r056 parts of vanadium, and 

 18"944- of oxygen, or 100 parts of the metal combine with 

 23*369 parts of oxygen, that is to say, with twice as much as 

 in the suboxide. 



3rdly, Vanadic Acid. — This is obtained by exposing vana- 

 date of ammonia to a heat near redness in an open platina 

 crucible, and stirring it occasionally. The vanadate decom- 

 poses, becomes at first black, and afterwards, in proportion 

 as it absorbs atmospheric oxygen, of a red brown colour, 

 wiiich, by cooling, becomes gradually pale, and finishes by 

 turning to a rust colour. The finer the sal ammoniac is 

 powdered, tlie paler is the colour of the acid. The acid 

 tlius obtained, when triturated, becomes of the colour of the 

 hydrate of iron, which forms on the surface of the metal im- 

 mersed in water. It is tasteless and inodorous; it reddens 

 the colour of moistened litmus paper. As soon as it is red 

 hot it (uses. In this stale it sustains a white licat without 



losing 



