|82$.] $eientific Notices — Mineralogy. 23$ 



Mineralogy. 

 2. Professor Berzelius^s Researches on Molyhdana. 



In studying the properties of molybdaena, M. Berzelius ha$ 

 found that this metal, of which we knew only the purple oxide^ 

 produced by drying the blue oxide, and molybdic acid, has 

 two salifiable oxides, whose saline combinations were till noMf 

 unknown. The deutoxide may be procured by digesting sji 

 mixture of molybdic acid, metallic molybdeena, 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 

 molybdsena. This hydrate is very soluble in water. When 

 it is washed, the water, after having removed the saline sub- 

 stances 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. Tl'ie 

 hydrate dissolves in acids, and gives salts whose solutions a)fe 

 yed, but which, when evaporated to dryness, 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 

 lime 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 hydrochloiric 

 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 appears 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 observed in the hydrate of the peroxide of 

 iron, and the protoxide of chrome and of zircon. The anhydrous 

 protoxide is insoluble 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 compound colour of green, black, and brown, though some- 

 times they assume a fine purple colojir. The fluate of the pro- 

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

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



In order to form the protoxide of molybdaena, we may make 

 •use of zinc in the place of the amalgam of potassium ; but the 

 protoxide then retains the oxide of zinc iu a very obstinate 

 manner. 



