Heroes of Science: ChemistsMuir, M. M. Pattison (Matthew Moncrieff Pattison)
History
Heroes of Science: Chemists
Muir, M. M. Pattison (Matthew Moncrieff Pattison)
Chemistry -- History; Chemists
In his first experiments on the effect of the electrical current on potash
and soda, Davy used strong aqueous solutions of these alkalis, with the
result that hydrogen and oxygen only were evolved. He then passed the
current through melted potash kept liquid during the operation by the use
of a spirit-lamp, the flame of which was fed with oxygen. Much light was
evolved, and a great flame appeared at the negative pole; on changing the
direction of the current, "aeriform globules, which inflamed in the air,
rose through the potash."
On the 6th of October 1807, a piece of potash was placed on a disc of
platinum, which was made the negative pole of a very powerful battery; a
platinum wire brought into contact with the upper surface of the potash
served as the positive pole. When the current was passed, the potash became
hot and soon melted; gas was evolved at the upper surface, and at the lower
(negative) side "there was no liberation of elastic fluid, but small
globules, having a high metallic lustre, and being precisely similar in
visible characters to quicksilver appeared, some of which burst with
explosion and bright flame as soon as they were formed, and others
remained, and were merely tarnished, and finally covered by a white film
which formed on their surfaces."
When Davy saw these metallic globules burst through the crust of fusing
potash, we are told by one of his biographers, "he could not contain his
joy, he actually bounded about the room in ecstatic delight; and some
little time was required for him to compose himself sufficiently to
continue the experiment."
This was the culminating point of the researches in which he had been
continuously engaged for about six years. His interest and excitement were
intense; the Bakerian Lecture was written "on the spur of the occasion,
before the excitement of the mind had subsided," yet, says his
biographer--and we may well agree with him--"yet it bears proof only of the
maturest judgment; the greater part of it is as remarkable for experimental
accuracy as for logical precision." But "to every action there is an equal
and opposite reaction:" immediately after the delivery of the lecture, Davy
was prostrated by a severe attack of illness, which confined him to bed for
nine weeks, and was very nearly proving fatal.
That the phenomenon just described was really the decomposition of potash,
and the production of the metal of which this substance is an oxygenized
compound, was proved by obtaining similar results whether plates of silver,
copper, or gold, or vessels of plumbago, or even charcoal, were used to
contain the potash, or whether the experiment was conducted in the air, or
in a glass vessel from which air had been exhausted, or in glass tubes
wherein the potash was confined by mercury. The decomposition of potash was
followed within a few days by that of soda, from which substance metallic
globules were obtained which took fire when exposed to the air.
Public-domain text, read in full here on John Shaqi.
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