EXPERIMENTS ON MOLYBDENA. IgQ 



blue: but many ^precautions were necessary to attain this Blue oxide, 

 result, because the surface passed very readily to a higher 

 degree of oxidation, and quickly reddened. On this blue 

 mass I poured cold water, which partly dissolved it; and by Dissolved ia 

 boiling I completed the solution, which was equally of a ^^^^'■• 

 blue colour. 



When the crucible, in heating it more strongly, passed Exposed to a 

 to a deep red, the metal quickly began to burn, putting on 8"^^*^^^ »»«^'* 

 likewise a deep red appearance. At this degree of heat it 

 kept its deep blue colour. The fire being increased, the 

 metal was brought nearly to a white heat, and after cooling, 

 its surface, to the depth of a few hnes, was of a blueish 

 white; nearer the centre it was of a blue inclining to vio- 

 let ; and the nucleus was violet inclining to brown, like the 

 matter obtained in decomposing molybdate of ammonia by 

 heat. The metallic mass, which had little consistency till 

 the action of the fire had given its surface a white colour, 

 became more compact and tenacious, so that it was diffi- 

 cult to crumble it between the fingers. On urging the fire Add formed, 

 the whole surface became enveloped by the raolybdic acid 

 that was formed ; and this acid gradually increased in quan- 

 tity, till at length it entered into fusion. 



These phenomena evidently indicate different degrees of Difterent de- 

 oxidation. The brownish oxide may be considered as the ^/^^s of oxida.* 

 first degree. The violet brown oxide is very probably at the 

 same degree of oxidation, as that obtained by exposing the 

 molybdate of ammonia to a red heat. The blue oxide so- 

 luble in water seems to contain a larger quantity of oxigen ; 

 while the blueish white oxide may be considered as a mix- 

 ture of the blue oxide with white oxide, the last of which is 

 probably nothing but molybdic acid, that fuses and sub- 

 limes at a higher heat. Thus these different oxides may be Thair order, 

 arranged in the following order : the light brown, the violet 

 brown or violet, the blue, and the white. 



Of these oxides the blue chiefly attracted ray attention. Blue chioflj- 

 jnore particularly on account of the diffeveut manners, in noticed. 

 which it may be produced by oxidation and diaoxidation, iu 

 the treatment of molybdena by acids, alkaline sulphurets, 

 tnetallic solutions, &c. 



IHxp. 



