The Life of Sir Humphry Davy, Bart. LL.D., Volume 1 (of 2)Paris, John Ayrton
Science
The Life of Sir Humphry Davy, Bart. LL.D., Volume 1 (of 2)
Paris, John Ayrton
Chemists -- England -- Biography; Davy, Humphry, Sir, 1778-1829
It has been already stated, that Davy had no sooner decomposed
the fixed alkalies than he proceeded to effect an analysis of
the earths; but his results were indistinct: they could not,
like the alkalies, be rendered conductors of electricity by
fusion, nor could they be acted upon in solution, in consequence
of the strong affinity possessed by their bases for oxygen. The
pursuit of the enquiry then demanded more refined and complicated
processes, than those which had succeeded with potash and soda.
The only methods which held out any fair prospect of success
were those of operating by electricity upon the earths in some
of their combinations, or of converting them, at the moment
of their decomposition, into metallic alloys, so as to obtain
presumptive evidence of their nature and properties. Such, in
fact, was the line of enquiry in which Davy was deeply engaged,
when he received from Professor Berzelius of Stockholm a letter,
announcing the fact that he had, in conjunction with Dr.
Pontin, succeeded in decomposing baryta and lime, by negatively
electrising mercury in contact with them, and that, by such
means, he had actually obtained amalgams of the earths in
question.
Our philosopher immediately repeated the experiments, and with
perfect success. After which he completed a series of additional
experiments, which fully established the nature of these bodies,
and the analogies he had anticipated. These results formed the
subject of a memoir, which was read before the Royal Society on
the 30th of June 1808, and entitled, "Electro-chemical Researches
on the Decomposition of the Earths: with Observations on the
Metals obtained from them, and on the Amalgam of Ammonia."
He commences this paper by enumerating the several trials he
had made to effect the decomposition of these bodies; such as,
First, by electrifying them by iron wires under the surface of
naphtha, with a view to form alloys with iron and the metallic
bases of the earths. Secondly, by heating potassium in contact
with the alkaline earths, in the hope that this body might detach
the oxygen from them, in the same manner as charcoal decomposes
the common metallic oxides. Thirdly, by submitting various
mixtures of the earths and potash to Voltaic action, with the
idea that the potash and the earths might be deoxidated at the
same time, and entering into combination, form alloys. Fourthly,
by mixing together various earths with the oxides of tin, iron,
lead, silver, and mercury: a mode of manipulation suggested
by the results of his previous experiments on potassium, in
which he found that when a mixture of potash and the oxides of
mercury, tin, or lead, was electrified in the Voltaic circuit,
the decomposition was very rapid, and an amalgam, or an alloy of
potassium, was obtained; the attraction between the common metals
and the potassium apparently accelerating the separation of the
oxygen.
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