210

Faraday's Researches

which, is assumed,, as far as I can judge, to a greater degree
in dilute sulphuric acid than in pure water. The power, there-
fore, of acids, alkalies, salts, and other bodies in solution, to
increase conducting power, appears to hold good only in those
cases where the electrolyte subject to the current suffers de-
composition, and loses all influence when the current transmitted
has too low an intensity to affect chemical change. It is
probable that the ordinary conducting power of an electrolyte in
the solid state (155) is the same as that which it possesses in the
fluid state for currents the tension of which is beneath the due
electrolytic intensity.

720. Currents of electricity, produced by less than eight or
ten series of voltaic elements, can be reduced to that intensity
at which water can conduct them without suffering decom-
position, by causing them to pass through three or four vessels
in which water shall be successively interposed between platina
surfaces. The principles of interference upon which this effect
depends will be described hereafter (745, 754), but the effect
may be useful in obtaining currents of standard intensity,
and is probably applicable to batteries of any number of pairs
of plates.

721. As there appears every reason to expect that all elec-
trolytes will be found subject to the law which requires an
electric current of a certain intensity for their decomposition,
but that they will differ from each other in the degree of intensity
required, it will be desirable hereafter to arrange them in a
table, in the order of their electrolytic intensities. Investiga-
tions on this point must, however, be very much extended,
and include many more bodies than have been here mentioned
before such a table can be constructed. It will be especially
needful in such experiments to describe the nature of the elec-
trodes used, or, if possible, to select such as, like platina or
plumbago in certain cases, shall have no power of assisting the
separation of the ions to be evolved (648).

722. Of the two modes in which bodies can transmit the
electric forces, namely, that which is so characteristically ex-
hibited by the metals, and usually called conduction, and that in
which it is accompanied by decomposition, the first^appears
common to all bodies, although it occurs with almost infinite
degrees of difference; the second is at present distinctive of
the electrolytes. It is, however, just possible that it may here-
after be extended to the metals; for their power of conducting
without decomposition may, perhaps justly, be ascribed to theirodes which is referred to further on in this part (776), and