■262 EXPERIMENTS ON M0LYBDEN.4. 



anew a precipitate of a reddish brown colour. All these 



' precipitates were decomposed by an excess of acid, a blue 



solution was formed, and nothing remained at bottom but 



sulphur of a brownish gray colour containing a little molyb- 



dena. 



Sulphuretted Exp. 44. Two phials were connected togjether as in 



hidrogen gas ,,r i r » t i • i i 



passed into a VV ou lie s apparatus, in one, which served as a receiver, 



solution of mo- ^j^g^g was a solution of one drachm of molybdic acid in 



lybdicacid. ., n . • ,^ .^ ^ „ 



eight ounces oi water: in the other there was an ounce of 



sulphuret of lime with eight ounces of watey, and sulphuret- 

 ted hidrogen gas was evolved. As soon as the eras began to 

 pass through the solution, this assumed a reddish brown co- 

 lour, which became deeper and deeper, but still continued 

 clear. I took a little, which smelled strongly of sulphuret- 

 ted hidrogen, added to it some muriatic acid, and a blackish 

 precipi tate was formed. At the expiration of four and twenty 

 hours the whole of liie solution became a little turbid ; and 

 after exposure to the air for twelve hours in shallow vessels 

 it was completely turbid, opake, and of the colour of mud. 

 Heated afterward to ebullition, it resumed its clearness and 

 colour, except that it was a little more inclining to yellow. 

 The froth that formed during the boiiuig was of a fine red- 

 dish yellow, like tincture of saffron. While it was evapor- 

 atinc' to dryness by a moderate heat, a smell of sulphuretted 

 hidiogeh continued to be given out, and toward the end a 

 great deal of ammoiiia was evolved. 

 Brown resl- The residuum, weij^hing fiity-five grains, was of a light 



duumexamin brown chocolate colour, and e .'n'lbited the following proper- 

 ties. 1. Ten grains being exposed to a moderate heat, a 

 pretty lar2,e quantity of ammonia was evolved, accompanied 

 with a smell of sulphureUed hidrogen. This smell alone was 

 perceived when the heat was increased: at length sulphu- 

 rous acid was given out, and the matter assumed a blueish '' 

 black colour. . It now weighed eight grains, was insoluble 

 in water, a.'d in the acid a little concentrated by a mean 

 temperature. 'I hvown into aredhot crucible, it immediately 

 became red, sulphurous add vapours were expelled, and it 

 melted. Th s was molybdic acid. 2. Ten grains of the 

 residuum put into a drachm of muriatic acid, and heated to 

 ebuUitioD, gave out but little sulphuretted hidrogen; and 



formed 



