Page:Proceedings of the Royal Society of London Vol 1.djvu/299

Rh ﬂuid, but a formation of small globules, having a bright metallic splendour and a perfect resemblance to quicksilver ; but they tarnished rapidly at their surface, and were in general soon covered by a white ﬁlm. but occasionally burned with explosion and a white ﬂame.

These globules were soon proved, by numerous experiments. to be a peculiar inﬂammable principle, the basis of potash.

The platina used, as the medium, for communicating the electric power. was proved not to have contributed otherwise to the result than as a conductor: for by substituting other conductors, as copper. silver, gold, plumbago. or charcoal, the same substance was formed by means of them. Its formation was also independent of the presence of air. as it took place equally under an exhausted receiver.

Soda. when acted upon in the same manner. and under similar circumstances, exhibited analogous results; but it required far greater intensity of action, and could not be decomposed in pieces which exceeded ﬁfteen or twenty grains in weight.

That the substances thus produced were evolved by the decomposition of the alkalies. was proved by careful examination of the gas extricated from the upper surface, which was found to be pure oxygen; and again proved synthetically. by ascertaining that they absorbed oxygen gas. to which they were exposed, and that the compounds resulting were, in fact. the respective alkalies that had been employed for their formation.

The aﬂinity of the base of potash for oxygen is such. that its metallic lustre very rapidly tarnishes in the atmosphere. by the formation of a white crust, which, by attracting moisture. is soon converted into a saturated solution of potash.

With the base of soda the phenomena are perfectly analogous, but less rapid; and when either of them is heated in oxygen gas, a rapid combustion. with brilliant white ﬂame, is produced. Oxygen gas is absorbed in this procms. and nothing emitted to affect the purity of the residual air.

It appears, then. says Mr. Davy. that in these facts there is the same evidence for the decomposition of potash and soda into oxygen and their peculiar bases, and for their recomposition, that there is for the decomposition and formation of any metallic oxide. or of the sulphuric or phosphoric acids.

In the analytic experiments no substances are present but the al- kalies and a minute portion of water, which, in its common form. seems in no other way essential to the result, than by rendering them capable of becoming ﬂuid, and conductors at a lower temperature than that at which their combustible bases burn; for if the quantity of water be increased, no such result is obtained.

These bases seem to be repelled, as other combustible substances, by positively electriﬁed surfaces, and attracted by negative surfaces, and hence are formed at that side in the electric circuit.

The properties of these bodies are such. that in the ﬁrst place it is extremely difﬁcult to preserve them, and to conﬁne them for experi- ments; such is their afﬁnity for oxygen, that they act on almost

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