254 EXPERIMENTS ON MOLYBE|ENA. 



of I'Sd, and left for twenty-four hours at an ordinaiy lem- 

 perature. The acid did not exert the slightest action on 

 the riietal. At a moderate heat a large quantity of sulphur- 

 bus acid Avas evolved, the liquor became of a yellowislt 

 lirown colour, and it assumed a sirupy consistence. It was 

 ihen diluted with four times as much water, and became of 

 a brownish yellow. After standing some time a little mo- 

 lybdena was deposited, which had not been dissolved. The 

 liquor having remained some hours in contact with the me-> 

 tal, it gi'adually turned green, and afterward blue: but the 

 most remarkable circumstance was, that part of the blue 

 oxide precipitated itself in the form of a very fine powder. 

 The cause of this phenomenon deserves inquiry. 

 Converted into This experiment tetiches us, that the inolybdena had been 

 "' changed by the action of sulphuric acid into a yellow oxide^ 

 containing more oxigen than the green and the blue, which 

 passed to the state of green oxide in consequence of a dis- 

 oxidation produced by the contact of irietallic raclybdenaoi 

 With nitric Exp. 30. In treating on the oxigenatibn of molybdena, 



*'■*"• I have ali'eady had occasion to say something of the action 



of nitric acid on this metal. The experiments I shall re-( 

 late will serve as a continuation. Ten grains of powdered 

 molybdena were put into two drachms of nitric acid diluted 

 with an equal quantity of water. At the expiration of a 

 quarter of an hour there was a slight evolution of nitrous 

 gas, and a pale red solution was formed. To accelerate the 

 action of the acid I employed a gentle heat, when the mo- 

 lybdena soon disappeared, and the liquor assumed a yel- 

 lowish brown colour with a tinge of red. I added ten 

 grains of molybdena two different times; and when I had 

 added the last ten grains, the liquor, which had been clear, 

 grew turbid, and became of a carnation red. This, added 

 to a slight evolution of nitrous gas,^led me to conclude, that 

 the acid was completely saturated. After standing a little 

 ^ while, blue oxide was perceived to form at the bottom of 

 the vessel, where a little molybdena still remained undis- 

 solved: a phenomenon similar to that observed in the solution 

 by sulphuric acid. Twenty-four hours after, the luatter 

 that rendered the liquor turbid was separated, and it com- 

 ported itself in all respects like molybdic acid. 



A sola- 



