Intelligence and Miscellaneous Articles. 395 



ON THE VANADIATE OF LEAD AND THE DOUBLE VANADIATE 

 OF LEAD AND COPPER. BY M. IGNACE DOMEIKO. 



The formation of secondary porphyry of Chili, which has been 

 already remarkable for specimens of the native amalgam of Arque- 

 ros, and of iodide of silver of Algodones, also contains a very rich 

 formation of vanadiate of lead and of copper. 



The mine in which these specimens were discovered is twelve kilo- 

 metres to the east of the silver mines of Arqueros, and is known by 

 the name of the Mina Grande, or Mina de la Marqueza, and was con- 

 sidered as one of the richest silver mines in Chili. A miner who 

 was about to recommence working the mine, found a heavy yellow 

 mineral, which he brought to Coquimbo for analysis. It was found 

 by M. Domeiko to be very poor in silver, but contained vanadium. 



This mineral is of a dirty yellow colour, sometimes of a sulphur- 

 yellow, or slightly orange or greenish ; its powder is of a yellowish 

 white colour ; its texture is compact, sometimes slightly earthy, and 

 sometimes of a weak resinous lustre. It contains numerous irregular 

 cavities, the interior of which is always incrusted with a brownish 

 matter, often consisting of globular concretions ; the mass sometimes 

 exhibits greenish earthy particles, coloured by carbonate of copper, 

 and also white carbonate of lead. 



Before the blowpipe, the mineral fuses with intumescence into a 

 gray metallic scoria, slightly frothed, and giving a blue colour to the 

 flame. On charcoal, with the addition of carbonate of soda, there 

 are obtained a perfectly malleable button of lead and a yellowish 

 gray scoria ; when melted on a platina wire, with the salt of phos- 

 phorus, it yields a transparent bead, which assumes a fine green 

 colour in the interior flame, and becomes yellowish brown in the ex- 

 terior flame ; when heated in the matrass, it yields a little water 

 derived from the argillaceous gangue ; nothing sublimes in the open 

 tube. 



Dilute nitric acid dissolves it readily, even when cold, without 

 producing either eff^ervescence or nitrous vapours, and leaves only 

 a residue of brownish or reddish gelatinous matter. Acetic acid has 

 no action upon it. The action of sulphuric acid determines the 

 absence of fluorine. 



The process which succeeded best in analysing this mineral was 

 the following : — 



The mineral reduced to an impalpable powder is treated with cold 

 dilute nitric acid, and digested for 24 hours ; it is then to be gently 

 heated and filtered to separate the ferruginous clay, unacted upon. 

 The chlorine is to be determined by nitrate of silver, the excess of 

 which is to be precipitated by a little hydrochloric acid. The greater 

 part of the lead is then to be precipitated by sulphuric acid ; the 

 filtered liquor is to be largely diluted, and sulphuretted hydrogen 

 is to be passed through it cold, and the operation is to cease as soon 

 as the lead and copper are precipitated ; filter and precipitate the 

 arsenic by saturating and repeatedly heating the solution. Evapo- 

 rate the filtered liquor to dryness ; treat the residue with hot dilute 



