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OXYGENATION.

When alkalies dissolve metals, the latter are alwaysoxygenated at the expense of the water, which holdsthe alkali in solution; thus when lead and copper aredissolved, the metals combine with the oxygen of thewater, while its hydrogen unites to the oxygen of theatmosphere and forms water; hence no hydrogengas appears.

The oxygenation of metals and other substancesby heat and air is easily explained on the same prin-ciple ; the metals, &c. unite with the oxygen of thewater contained in atmospheric air, while the hydro-gen of the water combines with the oxygen of theair, and forms a quantity of water equal to that de-composed.

This explanation is clearly proved by an experi-ment of Mr. Bergman on the regulus of manganese,which if kept in a dry place, retains its metallicsplendour, but if exposed to moisture, is soon oxyge-nated, and loses its lustre.*

It is further confirmed by the authority of thedistinguished Mr. Scheele, who says that “ the wa-ter contained in common atmospheric air is the chiefcause of the ignition of pyrophorus,” which he pro-ved by the following experiment.

* Clicm. Essays, Vo!. II. p. ao6 and 107. Eng. trans.