J35 EXPERIMENTS ON MOLYBDENA. 



being tlirowii out, I conducted the oxige;iation jn a tall ves- 

 sel, which I placed first on sant), and afterward in a cruci- 

 ble, the sides aijd bottom of which were coated with chalk. 

 By this process I obtained ninety grains of molybdic acid, 

 •which indicate fifty parts of oxigen to a hundred of metal; 

 80 that 100 parts of molybdic acid would consist of 66 6? 

 metal and 33*33 oxigen. 



The regulus of molybdena, which I had obtained in iTiy 

 preceding experiments, afforded me another mean of verify- 

 ing the results. 

 Experiment by Exp.'^O.ri hundred grainsof the metallic molybdena of expe- 

 acidifying the rimentlS were reduced to very tine powder, put into a porce« 

 metal itself. , . , ... ■ i ,• ■ i i t j 



lam capsule, and thirteen drachms oi pure i.Uricacid added. 



An extraordmary elfervescence took place, and a great deal 

 of nitrous gas was evolved. On evaporating, the matter, 

 which was at first of a brownish yellow, passed gradually 

 to a whitish yellow. In drying it became orange, and even 

 blue in those places where the heat was the strongest. Af- 

 ter it was well dried, and collected together, it was fused in 

 a glass; and its weight was found to be increased thirty- 

 four grains, which indicates 25*37 parts of oxigen in 100 of 

 molybdic acid. It was thoroughly crystalline, and formed 

 crystals of a silver white inclining to gray. 



Variation in The change of colour just mentioned, which has not been 



the proportion remarked before, indicated a variation in the proportion of 



of oxigen indi- . , . , i , , i 



cated oxigen to metal. It appeared to me probable, that a por- 



Was it owing tion, though small, of the charcoal, which had been 



tochar-oal. mingled with the molybdena to promote its reduction, had 



combined with it, produced the phenomena observed during 



the oxigenation, and changed the proportion of the oxigeta 



to the metal. 



Tv7o attempts Exp. 21. To verify this suspicion, I thought it necessary 

 to ascertain this iq repeat the trial, employing molybdena that I had reduced 

 by simply placing ihe mass to be reduced in the midst of 

 powdered charcoal, without having triturated and mixed 

 them together. The experiment failed twice. The first 

 time the eifervfescence and swelling up on pouring the nitric 

 acid on it were so great, that the matter ran over the sides of 

 the vessel : and the second, though the icid had been di- 



, luted. 



