EXPERIMENTS ON MOLYBDENA, J219 



^reat quantity of larger scale's, likewise of a violet colour, 

 and of a very fine metallic lustre. The outiide of the mass 

 was in 2;reat part covered with scales also, but smaller, and 

 exhibited a very pretty changeableness of colour. The up- 

 per part, which had been in contact with the charcoal dust, 

 displayed some reflections of an indigo blue. The outside of 

 the crucible was spotted with green in several places. 



Several circumstances in the preceding experiment indi- Fire apparently 

 I r not strong 



catc, that the mass would have become more soft and com- enough. 



pact, if it had been subjected to a more violent fire. In Greater heat 



consequence I took a similar quantity of molybdate of am- enipWe<i- 



monia, and exposed it to the action of the most violent fire 



for an hour. After cooling I found a mass weighing five Result. 



drachms in every respect similar to the preceding; except 



that it appeared a little more compact, and the fissures were 



filled with scales, which were more crystalline and in larger 



quantity. These scales, examined with a lens in a strong 



light, resembled polished false gold ; as the largest did when 



viewed by the naked eye. 



As the masses obtained in the four preceding experiments Reasons for 

 had a specific gravity varying from 4:5 to 5-67 according to producTmetat 

 their different densities, and this is the specific gravity as- lie molybdena: 

 signed by many to metallic molybdena; as besides, on heat- 

 ing them red hot in contact with air, or with nitric acid, in 

 which case oxigengas is evolved, they afforded molybdic acid ; 

 and lastly as they had a metallic aspect; I was induced to 

 consider them as reguli of molybdena, particularly as no one 

 had ever yet spoken of such an oxide. But subsequent ob- but it was a pe- 

 servations tanght me, that these masses were molybdena in a '^ lar oxi e, 

 peculiar state of oxidation, and that by the processes I had 

 Jjitherto followed it would be impossible for me to obtain 

 molybdena in the metallic state. It was necessary therefore, 

 that I should attempt its reduction by other means. 



Exps. 11, 12, and 13. I took four drachms of molybdate Attempts to re 

 of ammonia, similar to the two masses obtained in the pre- inglato aToft' 

 ceding experiments; powdered it; mixed it with olive oil, so paste vrith oil, 

 as to a^ake^a thick pap ; put it into a cruci|)le; and heated it 

 till the oil was burned. It was then pressed down ; covered 

 uith a stratum of charcoal powder, and over this a little pow- 



VoL. XX — June, 1 80S. K dered 



