lag Method of extracting Molyldic Acid 



molybdena ; or there was i'onned acidulous molybdate- of 

 potash which was not decomposed ; or only a little niolyb- 

 dic acid was separated ; or there remained in the liquid too 

 large a quantity of acid, which could be separated only in- 

 completelv and with difficulty. In this unfavourable state 

 of thinsfs I thought of several means for decomposing the 

 molybdate by the help of double affinities, but 1 was not 

 able by any of the known means to separate the acid com- 

 pletely from the alkali, I thereloie resolved to recur to the 

 old method, which consists in oxygenating the sulphurct by 

 nitric acid, taking care to correct the process by separating 

 the greater part of the sulphur by calcination. Bv this pre- 

 liminary separation of the sulphur a great quantity of the 

 acid is saved, and the labour is considerably shortened. 

 I consequently proceeded to calcination in the ibllowing 

 manner. 



Experiment VI. 



Five ounces and a half of sulphuret of molybdena in fine 

 powder, and which were perfectly pure, a few small pai ticks 

 of quartz and oxide of iron excepted, were introduced into 

 a large Hessian crucible, which, lor the 2,reater conveni- 

 ence, was placed obliquely in a furnace and surrounded by 

 charcoal. When the matter was red it was stirred inces- 

 santly, and in turns, by me and my friend M. Haberle, to 

 whom I was indebted lor the molybdena employed in these 

 difi'erent experiments. During the first hour, and before 

 the greater part of the sulphur was dissipated, the matter 

 retained its lightness : it then united into a mass, and its 

 black colour passed successively to gray, reddish gray, and 

 then to whitish gray. 



When the whole sulphur was driven off, which required two 

 hours, the mass by an increase of heat coagulated more and 

 raore, and even began to fuse at the bottom of the crucible, 

 and it appeared bv the vapour which rose that the molybdena 

 was volatilizing. Having maintained a moderate fire for half 

 an hour, I took the crucible from the fire and examined the 

 matter. It had a whitish gray colour, exhibited here and 

 there splendour and a crystalline form, and weighed a little 

 more than four ounces ; which approaches nearer to the 0*23 

 of sulphur which Lampadius said he found in molybdena 

 than the proportion of Kirwan, which is 0'o5. The sen- 

 sible metallic taste of the calcined matter, its brilliant and 

 crystalline aspect, and the experiments made by Ilsemann* 



• Creil's Chemische Annalen 17S7, vol. i. p. 410. 



and 



