ON THE THEORY OF SOLUTION. 335 
But it should not be forgotten that a great many purely chemical 
facts—in the first place the great generality and regularity of the 
chemical reactions of electrolytes as used in analytical chemistry, in 
opposition to the variability and irregularity of the behaviour of non- 
electrolytes, especially of organic bodies—have found their first explana- 
tion in the theory of electrolytic dissociation. The objection against this 
theory, that if the ions of saits exist ina free state this would not be 
any ground for the law of constant proportion between acid ions and 
metals, is easily refuted. For, according to Faraday’s law, all chemically 
equivalent amounts of positive and negative ions are charged with equal 
amounts of electricity ; in an electrically neutral solution, as all ordinary 
solutions are, there cannot but exist an exact equivalent number of 
positive and negative ions. We see, therefore, the law of Faraday con- 
nected in the closest manner with Richter’s law of chemical equivalents ; 
if the one holds good, the other must also hold good, and vice versé. 
Professor Armstrong has asked why water does not split into ions, 
while hydrogen chloride, a body similar to water, does. But has Pro- 
fessor Armstrong forgotten that liquid hydrogen chloride, like pure 
water, is an insulator for the electric current, as was found long ago by 
Gore, an observation afterwards confirmed by Bleekrode? It has been 
stated by F, Koblrausch that at ordinary temperatures no pure liquid is 
a good electrolyte. The theory of Arrhenius is still in this point the only 
one which explains this strange fact; pure liquids do not conduct, 
because their molecules have no space to resolve themselves into ions. 
It is therefore not improbable that water would conduct electrolytic- 
ally if we could find a suitable solvent for it. An investigation in this 
direction would be of very great interest, but not without grave 
difficulties. 
To a certain, but very small extent, water too contains ions, namely, 
Hand OH. This is shown by the hydrolytic action of water on the salts 
of weak acids and bases, the amount of H or OH ions dissociated from 
these acids or bases being in such cases comparable with the amount of 
the same ions in water. Then the latter acts as a very weak acid or base, 
and the action follows the common law of masses, as J. Walker has shown 
(‘ Zeitsch. f. phys. Chem.’ iv. 319). 
Professor vAN ’T Horr stated his conviction that we were forced on 
theoretical grounds, thermodynamic as well as kinetic, to admit in dilute 
solutions a law corresponding to that of Avogadro, differing from this only 
in its bearing upon ‘osmotic’ instead of ‘ ordinary’ pressure. He insisted 
on the necessity of dissociation in the case of KCl as a consequence which, 
on this line of argument, it was impossible to escape from. On the other 
hand, an ordinary separation into free atoms was in evident contradiction 
to all we knew about them, as in the vapour of iodine and mercury. These 
objections become invalid when we admit a splitting up into ions, which 
by their enormous electrical charge ought to be widely different from what 
we might expect in ordinary atoms, and hence it is that Arrhenius’s ‘elec. 
trolytic dissociation hypothesis’ was at once most favourably received by 
the adherents of the ‘osmotic pressure theory.’ Since then both have 
become closely allied by the fact that the dissociated fraction, according 
to the last, agreed with that admitted by the first on wholly different 
rounds. 
a In reply to the objections raised by Professor Fitzgerald, it may be 
