On the heating effects of electricity and magnetism / W.R. Grove.

  • William Robert Grove
Date:
[1852]
Catalogue details

Licence: Public Domain Mark

Credit: On the heating effects of electricity and magnetism / W.R. Grove. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    4/6 (page 122)
    To make evident to the audience the relation of the electrical dis- charge to combustion and the fact that the terminals were themselves affected, the Voltaic arc was taken, first between silver and then between iron terminals ; in the first case a brilliant green coloured flame was produced, and in the second a reddish scintillation or spur fire effect, just as in the ordinary combustion of the metals. So with the discharge of Franklinic Electricity between the same two metals, a strip of silvered leather gave the bright green discharge, while a chain of iron gave the spur fire effect. The known transport of particles of the terminals from one pole to the other,— the different effects of different intervening media on induction as shewn in Faraday’s experiments,— the polar tension of such media, &c. were instances of the train of molecular changes consequent upon electrical action. Hitherto the polarity of the gaseous medium existing between the metallic or conducting terminals of the electrical circuit was only known as a physical polarity and not shewn to have an analogous chemical character with that existing in electrolytes anterior to elec- trolysis ; but Mr. Grove stated that in a recent communication to the Royal Society he had shewn that mixtures of gases having oppo- site electrical or chemical relations, such as oxygen and hydrogen, or compound gases such as carbonic oxide, were electro-chemically polarized or had their electro-negative and electro-positive elements thrown in opposite directions : thus if a silvered plate be made positive in such gases it is oxidized, if negative the dark spot of oxide is reduced ; and an experiment was shewn in which such a plate was thus oxidized and the spot reduced in gaseous media. Here, as in the other experiments, was an effect on the terminals and an effect of polarization of the intermedium. In the experi- ments hitherto shewn, solid terminals were used ; it became important to examine what would be the effect of liquid terminals, for instance water ; the spark or disruptive discharge of Franklinic Electricity was readily obtained from its surface, but hitherto no voltaic battery had been found to shew a discharge-at any sensible distance from the surface of water. Mr. Gassiot had procured to be constructed 500 cells of the nitric acid battery, the combination discovered in 1839 by Mr. Grove and first shewn at this Institution in the year 1840. The cells of this battery were all well insulated by glass stems, and as regards intensity of action it was probably far the most powerful ever seen. Mr. Gassiot had kindly lent this apparatus for the illustration of this evening’s discourse, and by its aid Mr. Grove was able to shew an experiment which he had first made when experimenting with Mr. Gassiot some time ago, and which produced the effect he had long sought for, viz. a quantitative or voltaic dis- charge at a sensible distance from the surface of water. The experiment was made as follows : — a platinum plate forming the anode of the battery was immersed in a capsule of distilled water, the temperature of which was raised. A cathode or negative terminal of platinum wire was now made to touch for a moment