EXPERIMENTS ON JWOLYBDENIf. Jgg 



Notwithstanding the molybdena here possessed all the pror 

 pertics, that characterize metals, lustre, compactness, and 

 even malleability, though in a slight degree, I could not ob- 

 tain a well fused metallic button by exposing afresh to the 

 most violent forge fire for two houi-s a piece of the mass al- 

 ready obtained, that weighed forty grains. A trial I after- Most success^ 

 ward made with two ounces of brown oxide was attended fusj,on!"^^ 

 with better success, than any I had yet obtained. I exposed 

 this oxide to the most violent fire, well kept up, but for one 

 hour only: and though the whole mass was not fused into a 

 button, yet in some parts appeared pieces of one or two 

 drachms, almost entirely fused, having a spherical surface, a 

 white metallic lustre, and a much greater consistency than 

 any mass I had yet obtained. On rubbing these metallic 

 parts against a very smooth piece of porcelain, they assumed 

 a lustre, which it would have been difficult to distinguish 

 from that of silver. I must observe too, that this lustre re- 

 mained for several days; while in my other trials it did not 

 continue an hour, probably owing to the moisture of the air. 



From the experiments hitherto related we may infer; ' General con- 



1st, That heat, in decomposing the molybdate of ammonia, <^^"'^'''"^' 

 causes the acid, in consequence of the disoxigenizin^ action 

 of the ammonia, to pass to a. slighter degree of oxidation, 

 and gives rise to a peculiar oxide, some of the external cha- 

 racters of which have been noticed in the account of the 

 Jlth, 12th, and 13th experiments. 



2dly, That the oxide and acid of molybdena are com- ' 



pletely reducible by the simple action of fire, when they are 

 plated in the midst of powdered charcoal, and that the metal 

 then appears of an ash gray colour : but that, this metal being 



grains, the least of which had the appearance of silver j and that the 

 sides of the crucible had a coating of the same colour. He did not ven- 

 ture to assert however, that these grains were entirely metallic ; for he 

 observed others which were either of a whitish gray, reddish, or blueish. 

 The following part of this essay, and what has already been said, will 

 show, that these coloured grains belong to the oxide, which has been 

 mentioned. Hielm, observing that molybdena rendered the colour of 

 other metals lighter, inferred, that its own colour was white. This infer- 

 ence is confirmed by my exp»",rimeuts. 



difficult 



