It appears that by friction the rubber obtains oxygen from the atmosphere, which is partly composed of that element. The oxygen combines with the amalgam of the rubber, which is of a metallic nature, much in the same way as the oxygen of the acid combines with the zinc in the Voltaic battery, and it is thus that the two electricities are disengaged.
CAROLINE.
But, if the electricities of both machines are similar, why not use the common machine for chemical decompositions?
MRS. B.
Though its effects are similar to those of the Voltaic battery, they are incomparably weaker. Indeed Dr. Wollaston, in using it for chemical decompositions, was obliged to act upon the most minute quantities of matter, and though the result was satisfactory in proving the similarity of its effects to those of the Voltaic battery, these effects were too small in extent to be in any considerable degree applicable to chemical decomposition.
CAROLINE.
How terrible, then, the shock must be from a Voltaic battery, since it is so much more powerful than an electrical machine!
MRS. B.
It is not nearly so formidable as you think; at least it is by no means proportional to the chemical effect. The great superiority of the Voltaic battery consists in the large quantity of electricity that passes; but in regard to the rapidity or intensity of the charge, it is greatly surpassed by the common electrical machine. It would seem that the shock or sensation depends chiefly upon the intensity; whilst, on the contrary, for chemical purposes, it is quantity which is required. In the Voltaic battery, the electricity, though copious, is so weak as not to be able to force its way through the fluid which separates the plates, whilst that of a common machine will pass through any space of water.
CAROLINE.