PROOFS OF THE PROPERTIES OF COPPER.

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and the bottle immediately stopped without including any air.no solution will take place. On the contrary, if the bottle beleft open for some time, and then closed, a solution is effected,which is absolutely colourless, but turns blue on re-opening thebottle, beginning at the surface and gradually extending down-wards through the whole mass. Again, if this blue solution hasnot been too long exposed to the air, and fresh copper filings beput in, stopping the bottle again, the solution is deprived of allits tinge, and recovers its colour only hy the admission of air.And this effect may be produced repeatedly.

Rationale. ..Metallic copper, as such, is not acted upon byliquid ammonia, but is soluble when oxidated. This oxidationis effected by the influence of oxigen gas when atmospheric airis admitted. Hence, when the copper is no farther oxidatedthan is necessary for solution, this is colourless; but it acquiresa blue colour when the metal is oxidated in a higher degree. Itis also obvious that this azure colour is again destroyed by theaddition of more copper filings and exclusion of air, as the newlyadded metal deprives that which was contained in the solution inan oxidated state of its super-abundance of oxigen in order to bedissolved also in the liquid.

Experiment III.

Copper combines with phosphorus.

(Preparation of phosphuret of copper.)

Mix together equal parts of fine copper filings and glacialacid of phosphorus, add one-eighth part of charcoal-powder, andthen fuse the whole in a Hessian crucible. The product will bea metallic button of a whitish appearance, which sometimesexhibits the prismatic colours.