Eti>ERlMENTS ON MOLYBDENA» Q5.^ 



A solution of molybdena by nitric acid, made witbouf Solution in nj- 

 heat, became perfectly clear in a few hours, and of jj *''^^'"^ .w'^^' 

 yellowish brown inclining to red. It had a slightly acid 

 taste, that left behind it a bitterness with somewhat metal- 

 line. Part having evaporated by a gentle heat in a porce- 

 lain capsule, it left a pulverulent residuum of a dirty red- 

 dish yellow, which, being put into a small quantity of wa- 

 ter and shaken, was entirely dissolved, except a small por- 

 tion, that was molybdic acid. The solution vvas yellow in- 

 clining to red: and on being digested with metallic molyb- 

 dena it became blue. 



Twenty grains of powdered molybdena having been put 

 into a drachm of fuming nitric acid, an extremely vivid 

 effervescence took place, attended with an extrication of 

 red vapours, and the mixture became consolidated into a 

 mass of a light brownish red colour. Another drachm of 

 the same acid being poured on this, and moderately heated, 

 white molybdic acid was very readily produced. 



JExp. 31. The reddish solutions obtained in the pre- The nitric so- 

 ceding experiments being filtered, ammonia, cautiously amiued, 

 added, produced a flocculent precipitate of a brownish 

 red colour, which, having been washed and dried, j'ielded 

 a powder of a lighter hue interspersed with white and shin- 

 ing crystalline particles. Some of this powder was put into 

 a small quantity of water, at a moderate temperature, and 

 shaken, in which it all dissolved except a few small white 

 crystals. These crystals however were not molybdic acid, 

 for they were much more soluble, and had a much stronger 

 acerb taste. The solution of the brown powder was of a vi- 

 nous yellow colotir inclining to red. The water, with which 

 this powder was washed after its precipitation, had a deeper 

 colour, because the precipitate was more soluble after being 

 wetted. On adding ammonia, or potash, to the solu- 

 tion, a brown red precipitate fell down slowly once more. 

 This precipitate being treated with a solution of alkaline 

 carbonate, it was not attacked, but the white crystals were 

 dissolved with effervescence. Farther experiments are ne- 

 cessary, to determine the nature of the products formed in 

 this process. I shall here confine myself to the remark, 

 that the brown precipitate cannot be taken for the brown 



oxide 



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