M6 



tXPERIMETfTS ON MOLYEDENA. 



molybdena, and merely in mechanical union with the speci- 

 • mciis analysed. 



Forthe subsequent experiments I was desirous of procur- 

 ing some quantity of molybdic acid. The processes 1 em- 

 ployed are mentioned in another work, here therefore I shall 

 mtntion them briefly. 



II. Process /or ohtaining molybdic acid. 



To obtain the I took llf ounces of native molybdena, the quartz ad- 

 **^' ' herinj; to which was pretty well separated, and put it into a 



large crucible, which was placed obliquely on the fire. A 

 native sulphu- strong heat was first given, to kindle the sulphur, which was 

 ret roasted in afterward diminished, and the matter was roasted, stirring it 



an iiKlincd • ,, . , , , a , • ,• 



crueiWe. occasionally with a wooden spatula. A lai-ge quantity ot 



sulphurous acid was evolved, and the mass was entirely co- 

 vered with a crust of the purest molybdic acid, which was of 

 a lemon colour on the fire, and of the purest silvery white 

 when cold. By taking a little trouble, and using some pre- 

 cautions, the whole might thus have been converted into mo- 

 lybdic ncid : but as this would have required a great deal of 

 time and attention, I put an end to the process, when I per- 

 ceived, that the greater part of the sulphur was volatilized, that 

 a considerable quantify of molybdic acid was formed, and 

 that, on leaving it exposed to a lower degree of heat, the mass 

 began to agglutinate, and even to become fluid near the sides 

 of the crucible. By this operation I obtained S|- ounces of 

 a gray shining mass, perfectly crystalline, which was of a 

 * whitish gray colour when powdered. Half an ounce remain- 



ed adiiering to the sides of the crucible, which could not 

 easily be separated from it. 

 The. acid may The pure molybdic acid may be separated from the mass 

 b« separated by heating it with water, adding carbonate of soda till it 

 >\Mh an"exce^s Ceases to occasion effervescence, and afterward boiling it with 

 oi soda, or di- a litile excess of soda : or the separation may be efiected by 

 ^t.-stiiii' in am- ,. . , i- • j • .1 i ^ 



iv ,1 ii an'i pre- digesting the mass in pure liquid ammonia, the heterogeneous 



ci i'atingby parts, such as the quartz and oxide of iron, remaining undis- 

 txe^ll'mc th"J solved. On pouring nitric acid into the neutral solution, the 

 innmoniaby molybdic acid is thrown down. 'I'he molybdate of ammonia 

 '''^^' might be decomposed likewise by Are; in which case some- 



times 



