The Bakerian Lecture, on some chemical agencies of electricity ... From the Philosophical Transactions / By Humphrey Davy.

  • Humphry Davy
Date:
1807
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Licence: Public Domain Mark

Credit: The Bakerian Lecture, on some chemical agencies of electricity ... From the Philosophical Transactions / By Humphrey Davy. Source: Wellcome Collection.

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    munication with the same instrument do not by their agencies in the slightest degree affect the gold leaves. Solid pure potash and sulphuric acid made to combine in an insulated platina crucible produce no electrical appearances. A solid amalgam of bismuth and a solid amalgam of lead become fluid when mixed together: the experiment, I find, is con- nected with a diminution of temperature, but with no exhi- bition of electrical effects. A thin plate of zinc, after being placed upon a surface of mercury, and separated by an insu- lating body, is found positive, the mercury is negative: the effects are exalted by heating the metals ; but let them be kept in contact sufficiently long to amalgamate, and the compound gives no signs of electricity. I could mention a great number of other instances of pure chemical action in which I have used all the means in my power to ascertain the fact, and the result has been constantly the same. In cases of effervescence, in- deed, particularly when accompanied by much heat, the metallic vessels employed become negative, but this is a phenomenon connected with evaporation, the change of state of a body inde- pendent of chemical change, and is to be referred to a different law.* * The change of the capacities of bodies in consequence of the alteration in their volumes, or states of existence by heat, is a continually operating source of electrical effects: and as I have hinted, page 36, it often interferes with the results of ex- periments on the electrical energies of bodies as exhibited by contact. It is like- wise probably one of the sources of the capricious results of experiments of friction, in which the same body, according as its texture is altered, or its temperature changed, assumes different states with regard to another body. Friction may be considered as a succession of contacts, and the natural energies of bodies would pro- bably be accurately exhibited by it, if the unequal excitation of heat or its unequal communication to the different surfaces did not interfere by altering unequally their electrical capacities. Of the elements of flint glass, silex is slightly negative with
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