258 EXPERIMENTS ON MOLYBDENA. 



Succinic, tar- I had similar results v/ith .the succinic, tartarous, and 

 ^^1"*' tiT"^' citric acids: only I ohferved, that, in treating niolybdena 

 acids. with succinic acid, the liquor became green during evapora- 



tion.^ Acetic acid produced no efiiect on it cold ; but when 

 boiled, and the liquor reduced to about half, it assumed a 

 brownish yellow colour. Ammonia scarcely rendered the 

 solution turbid. 

 General con- From what has been said it appears : 



aSofTcids! 1^*- 'T'^''^' ^'h^^never molybdeaa is dissolved by acids, it 

 becomes oxided at their expense, and consequently can be 

 dissolved only by those acids, which, like the nitric, sulphu- 

 ric, oxigenized muriatic, phosphoric, and arsenic, are sus- 

 ceptible of several degrees of oxidation, and capable of 

 parting with oxigen, either at the common or a higher tem- 

 perature. 



Sdly. That by the action of acids niolybdena may be 

 brought to the state of blue oxide, and sometimes of brown, 

 the nature of which is yet to be exanjined. The phospho- 

 tic alone appears to produce a dift'erent state. 



3dly. That these solu ions can scarcely be considered as 

 salts, on accouat of the acid nature of the oxide of molyb- 

 dena. 



IX. Action of potash on the native fulphuret of molyhdena. 

 Potash with Exp. 37. On fifty grains of pure sulphuret of molyb- 



\lftKet of mo- ^^"^ ^ poured a lixivium containing two hundred grains of 

 Ijbdena. pure caustic alkali, evaporated to dryness, diluted the resi- 



duum in water, and "evaporated again. After repeating this 

 several times, J. separated the undissolved part by filtration, 

 washed, and dried it. The loss amounted to scarcely four 

 grains, and what remained liad the same ajipearance as be- 

 fore. On this I poured sulphuvic acid diluted in water, but 

 no sulphuretted hidrogen gas was evolved. The filtered 

 liquor has a strong taste of sulphurous acid; diluted sul- 

 phuric acid expelled from this a large quantity of sul- 

 'phuretted hidrogen gas; its colour, which was a 'pale 

 brownish yellow, changed to brownish red; and at the end 

 of a. few minutes a'fine brovvnish red precipitate was formed, 

 which gradually changed brown, and thence to a yellowish 

 brown; the liquor becoming a pale reddish brown. Th* 



precipitate'. 



I 



