134 Prof. Berzelius's Researches on Molybdaena. 



now unknown. The deutoxide may be procured by digest- 

 ing a mixture of molybdic acid, metallic molybdaena, and 

 sulphuric or hydrochloric acid, till the colour of the liquid 

 becomes a deep red. Instead of metallic molybdaena, we 

 may substitute metallic copper. The red liquid gives, with 

 ammonia, a rust-yellow precipitate, which is the hydrate of the 

 deutoxide of molybdaena. This hydrate is very soluble in 

 water. When it is washed, the water, after having removed 

 the saline substances, which caused its precipitation, begins to 

 dissolve the hydrate, and becomes yellow. It at last dissolves 

 it entirely, and the saturated solution is red. It reddens 

 turnsol. The hydrate dissolves in acids, and gives salts, 

 whose solutions are red, but which, when evaporated to dry- 

 ness, are almost black. 



The protoxide is produced when we macerate the solution of 

 a salt, with a base of the deutoxide, with mercury, and add, from 

 time to time, a liquid amalgam of potassium. The colour of 

 the liquid becomes deeper, and ends by growing black. Before 

 the introduction of the amalgam, we must add to it hydro- 

 chloric acid, in order to prevent a part of the deutoxide from 

 being precipitated before its entire reduction to the protoxide. 

 The black solution is then precipitated by ammonia, and the 

 black precipitate is the hydrate of the protoxide, which must 

 be well washed, and then dried in vacuo. The hydrate ap- 

 pears then under the form of a jet black powder. When 

 heated in vacuo, it gives out slowly its water, and afterwards, 

 at a temperature which approaches to that of brown-red, it 

 takes fire, and burns with scintillation. The barometer of 

 the air-pump is not affected by this phenomenon, which, in 

 other respects, is of the same nature as that which is observ- 

 ed in the hydrate of the peroxide of iron, and the protoxide 

 of chrome, and of zircon. The anhydrous protoxide is in- 

 soluble in acids. When heated in air, it takes fire, and burns 

 feebly, producing the brown oxide of molybdaena. The salts 

 of this oxide are black, and their dilute solutions have a com- 

 pound colour of green, black, and brown, though sometimes 

 they assume a fine purple colour. The fluate of the protox- 

 ide, for example, is a very fine purple, and the double fluates 

 with potash, soda, and ammonia, are of a rose red colour. 



