1871.] Dr.. A. Schrauf on Molybdates and Vanadates of Lead. 459 



orange. This salt, heated in a platinum spoon with tin-foil, gives a faintly 

 greyish-green solution. 



The analogy between the vanadate of lead from Schlettenbach (deche- 

 nite) and the vanadate from Windisch- Kappel (vanadiaite) goes still beyond 

 their chemical characters. I submitted both these minerals to the action 

 of the blowpipe, in order to find out, independently of my comparative 

 studies concerning eosite, the cause of the prompt decomposition of the 

 cabinet specimens from both these localities. 



A splinter of dechenite from Schlettenbach, heated in a glass tube, 

 emits, previously to its melting, a greenish -white vapour, not condensing 

 into water drops nor into any other deposit upon the cooler portions of 

 the tube. The presence of arsenic is manifested neither by its charac- 

 teristic smell nor by any specular sublimate. The mineral takes a darker 

 tint when heated, and assumes again its original tint by cooling. It melts 

 in the glass tube, without previous decrepitation, into a brownish-yellow 

 substance. Heated on charcoal, dechenite melts easily, and with ebullition, 

 into a hollow dark steel-brown globule, giving at the same time a slight 

 orange aureola and a whitish slag, including metallic granules. Fusing 

 with soda gives rise to a yellowish slag, including granules of metallic lead, 

 and to graphitic vanadium imbedded in the charcoal. The slag imbibed 

 with cobalt-solution and heated to redness, assumes a dirty greenish tint 

 and is surrounded by a greenish-yellow aureola, thus betraying the presence 

 of a rather notable quantity of zinc, not mentioned in M. Bergemann's 

 account of his analysis of dechenite. 



Among the vanadinites from Kappel, only the carnation variety B seems 

 to contain a notable proportion of zinc. Its tint darkens transitorily during 

 heating, it emits a faint vapour (of water) when heated in a glass tube, 

 without manifesting the presence of arsenic, and melts on charcoal into a 

 dark greyish-brown, steel-bright globule, proving hollow when the flame 

 of the blowpipe touches it. A notable aureola of oxidated lead appears, 

 together with a small quantity of a dark slag, including globules of lead 

 and graphitic vanadium, and assuming a green tint in contact with nitrate 

 of cobalt. 



The darker variety A exhibits the same phenomena when heated in the 

 glass tube or by the blowpipe-flame, only the remaining slag is dark 

 coloured, and only in one case among repeated experiments could I perceive 

 on it some faint traces of green coloration. Possibly this variety may 

 contain but a small proportion of zinc, as M. Damour has found only 2| 

 per cent, of this metal in the Peruvian descloizite. 



The results of the before-detailed investigations, leaving out of account 

 at present the subsequent crystallographical facts, may be resumed as 

 follows : — Of both the varieties of vanadinite from Kappel, the darker one 

 (A) contains but a small proportion of zinc, and may be assimilated to 

 the Peruvian descloizite ; the lighter one (B) is far richer in this metal, 



