M. Berzelius on Vanadium. 15 



tion of vanadate of potash or soda. The vanadate of ammo- 

 nia soon begins to deposit in colourless granular crystals. 

 A solution even of muriate of ammonia precipitates a great 

 portion ; but it is only by saturating the solution with this salt, 

 that all the vanadate can be separated. In fact, a very small 

 quantity does remain in solution; but it may be precipitated 

 by alcohol, or by adding first a hydrosulphuret, and after- 

 wards an acid ; nevertheless, I repeat, the quantity is very in- 

 considerable. The precipitate is to be washed, first with a 

 solution of muriate of ammonia, and afterwards with weak 

 alcohol, to separate the muriate of ammonia. Vanadate of 

 ammonia, dried at a temperature of from about 70° to 90° of 

 Fahrenheit, is a white powder. At a higher temperature it 

 becomes of a lemon yellow, by losing a little of its base. It is 

 but little soluble in cold water, but much more so in boiling- 

 water; in this case the solution is yellow, while that obtained 

 with cold water is colourless. This change of colour takes 

 place in a stopped bottle which is nearly full ; it does not there- 

 fore depend upon the formation of a bivanadate. In order to 

 purify this salt by repeated crystallizations, a litde ammonia 

 must be added to the boiling water in which it is dissolved ; 

 the solution then remains colourless, and the salt crystallizes 

 better by cooling. The white salt is never in regular crystals ; 

 it is always in crystalline grains, which are more or less large, 

 and form a coherent crust, which covers the surface of the 

 vessel. The crystallization is similar, whether formed by 

 spontaneous evaporation or by cooling; by the first method a 

 lemon-yellow crust is often obtained. When dry vanadate of 

 ammonia is treated in a covered crucible, the ammonia reduces 

 the acid, and on cooling a black oxide is obtained. This 

 happens because the heat begins by driving off a portion of 

 ammonia, without decomposing the acid ; there is therefore 

 produced an ammoniacal atmosphere in the crucible, and this 

 alkali reduces to the state of suboxide the portions of vanadic 

 acid which touch the crucible, and which are hotter than the 

 middle of the mass, where vanadate of vanadium is formed. 

 The quicker the heat, the greater is the quantity of suboxide 

 formed. When thrown into water, the mass almost always 

 becomes of a green colour. 



Bivanadate of Ammonia. — This salt is deposited by cooling, 

 in very small crystals of a deep orange-red colour. By spon- 

 taneous evaporation, larger, more regular and transparent cry- 

 stals are formed, and their red colour is much more intense. 

 Alcohol precipitates it completely in the state of a lemon- 

 yellow powder. 



Hupcrvanadate of Ammonia. — When a solution of the bisalt 



is 



