from 'Native Mohjldaia. #0! 



whole moisture was dissipated. During tiie evaporation T 

 observed no disengagement of nitrous gas, from wliich I 

 could conclude that there was in the residuum a little nio- 

 lybdena not vet aeiditied. I then boiled the residuvnn for 

 half an hour with a lev of carbonate of soda, alter which 

 there was added to the solution nitric acid to decompose it; 

 but I observed no precipitation of niolvbdie acid, though an 

 excess of nitric acid had been added. The solution had only 

 a metallic acid taste. On examining the residuum more 

 closely, it was found to be composed of alumine, oxide of 

 iron, and a few fragments of silcx, which, if I except the 

 oxide of iron contained in the sulphurated molvbdena, arose 

 in part from the molybdena and partly from the crucible. 



'Experiment XIII. 



The white precipitates of experiments X. and XI. were 

 put into 4n ignited crucible. By an increase of licat they 

 first entered into fusion, and were then volatilized and con- 

 densed, partly under the pulverulent form and partly under 

 the crystalline. By continuing the fusion the matter pene- 

 trated through the crucible. The fused matter was very li- 

 quid, and on cooling it fonned itself into a crystalline ra- 

 diant mass of a whitish gray colour having a slight metallic 

 splendour. In other respects it exhibited the same phaeno- 

 mena as pure molybdic acid. 



This last method furnishes a very short and occonomical 

 method of obtaining molybdic acid. There can be no doubt 

 that if the molybdena had been entirely free from matrix 

 the calcined mass would have entirely dissolved, except an 

 atom of iron, from which sulphuret of mol)bdena is ne\'cr 

 free, 



I was desirous also to try the separation of the molvLdic 

 acid by the help of ammonia. With this view I made the 

 jLoUowing expernnents. 



Experiment XIV. 



I digested for twelve hours, in a moderate heat, a gros of 

 the calcined mineral in line powder with half an ounce of 

 conce!itrated lupiid ammonia, shaking the matter from time, 

 to lime; after which the hcpior was filtered. It had still 

 a htr.>ng odour of ammonia. The half of it was decom- 

 posed by nitric acid, which precipitated from it inolvbdic 

 acid in abundance. The other half was evaporated in a 

 Muall porcelain capsule, aud then heated to a slight degree 

 of incandescence. The amm(mia was entirely dissipated, 

 and left a grayish blue residuum, which entered into fusion 



in 



