ON ELECTROLYSIS. 741 
Innumerable similar experiments suggest themselves, but it is need- 
less to specify any more of them at present. 
III. Quantitative Laws or ELecrrotysis. 
The main laws known at the present time concerning the passage of 
electricity through liquids may be denominated, (a) Ohm’s or Kohl- 
rausch’s, (b) Faraday’s two laws, (c) Joule’s, or Helmholtz’s, or Thom- 
son’s law. 
(a) Ohm's Law of Electrolytic Conduction. 
The researches of Kohlrausch and Nippoldt, and several others, give 
us very good grounds for asserting that, in all ordinary cases of electro- 
lytic conduction, Ohm’s law is at least approximately obeyed: currents 
being proportional to E.M.F. actually applied to the liquid. It is 
exceedingly important to test this law in liquids with the utmost accu- 
racy, as has been done for metals by a British Association Committee 
(Maxwell and Chrystal), but the research would be a very difficult one. 
We have seen reason for guessing that with violent currents the law may 
perhaps begin to fail, even if it be exact for weak currents; but on Max- 
well’s theory of light it can hardly be quite exact for any current, 
because the optical transparency of electrolytes shows that they behave 
as dielectrics to very rapidly alternating E.M.F.s. But the law is very 
nearly true any way, and this fact of itself is important, as showing that 
infinitesimal E.M.F.s can produce a current. 
Now if there were any chemical cling hetween the atoms taking 
part in conduction this could not be—a finite E.M.F. would be needed 
to tear them asunder; and this is what physicists mean by using the 
term ‘dissociation’ in this connection. The atoms are so free of one 
another that they must be either really or virtually dissociated. Not all 
the molecules of the compound need be in this condition, of course, only 
a certain percentage of them, and the conductivity of the liquid must 
depend upon the value of this percentage. It may be supposed nil in a 
perfectly pure homogeneous liquid like H,O; it may be supposed to be 
caused by the presence of foreign molecules (¢.g. of salt or acid); and it 
may be supposed to increase with rise of temperature. 
The transparency of an electrolyte may, however, be explained 
without assuming any violation of Ohm’s law, by supposing that the 
percentage of dissociated atoms is too small to perceptibly affect the 
properties of the liquid in bulk. On this hypothesis, rise of temperature, 
or other mode of increasing conductivity, might perhaps cause some in- 
crease in opacity ; moreover it is to be remembered that the transparency 
of electrolytes for long waves is possibly very small. 
(b) Faraday’s Two Laws. 
(1) The voltametric law. 
(2) The law of electro-chemical equivalence. 
Law 1 asserts that the amount of electro-chemical decomposition is a 
precise measure of the amount of electricity conveyed; i.e. that no 
electrolyte for which the law is true possesses a trace of metallic conduc- 
tivity ; or, that electrolytic conduction and chemical decomposition are 
precisely correlative. 
The law has been most exactly verified for nitrate of silver solution 
