Page:Proceedings of the Royal Society of London Vol 1.djvu/67

Rh decompose this ore, he had recourse to a process to which he was led by some instances he had before observed, in which a mixture of two compounds of the same ingredients, but in different proportions, remained insoluble, while a third substance seemed to operate upon at least one of these two compounds, and to produce the decompo- sition that was aimed at. The following is the manner in which he explains this operation:-When a metallic oxide A, for instance, containing 25 per cent. of oxygen, is in contact with the metallic oxide B, containing 10 per cent., they will each remain quiescent in their respective states: but if a solvent C, for which the substance B has no affinity at 10 per cent. of oxygen, but a powerful one at 15 or 20 per cent., comes to be added, then may the oxide A lend a part of its oxygen to B, in order to enable it to combine with the solvent C. Thus when phosphoric acid had dissolved all it could of the pulverized ore, its oxygen in the part undissolved was concen- trated, as it were, to the amount of about 20 per cent.; and all that which could not be dissolved, would, through a twofold affinity of copper for oxygen to the amount of 20 per cent., and of phosphoric acid for the oxide of copper of that degree of oxidation, yield up its entire share of oxygen, to favour the combinations which took place in the new ordcr, the only one which could exist among the sub- stances now present.

From the variety of experiments founded upon this reasoning, it has been gathered, that the copper in this ore contains much less oxygen than has ever been suspected in any oxide of copper; and that, from the quantity of the copper which was precipitated in the metallic state by iron, it appears to be combined in the proportion of only 11 per cent., the rest being pure copper, a state of metallic concentration of which no instance has as yet been observed in nature.

It is lastly suggested, that, considering not only the great purity of this ore, but also the singular facility with which this useful metal may be extracted from it, it will be found much superior to every copper ore hitherto discovered. It contains no iron and no sulphur; the absence of which latter is a peculiar advantage. It is hence strongly recommended to the proprietors of mines to be particularly attentive to this ore, which is said not to be uncommon in some parts of Cornwall, whereby they are likely not only to further their private advantage, but may also materially contribute to promote the public utility

This singular production has hitherto been found only in a small lake in Carniola, called Sitticher See, and has never yet been met