INTRODUCTION 17 



5. Electricity and Matter. While electrolytic solutions are thus of 

 great importance from a practical point of view, they have played no 

 less important a role in the development of our conceptions of the nature 

 of matter and the nature of chemical reactions. That electricity and 

 matter are intimately related was long since pointed out by Helmholtz 

 as a consequence of Faraday's Law. Since in electrolytes electricity and 

 matter are associated in definite and fixed proportions, and since matter 

 appears to be discrete in its structure, it follows that electricity also must 

 be discrete in its fundamental structure. Corresponding to the atoms, 

 the smallest subdivisions of elementary substances, we have the funda- 

 mental charge of electricity, the charge associated with a single univa- 

 lent ion, which represents the smallest known subdivision of the electric 

 charge. The development of the mechanics of the atoms in the last two 

 decades has greatly enlarged our knowledge of the fundamental relation 

 between electricity and matter. The fundamental charge of electricity, 

 the charge associated with the negative electron, is objectively as real as 

 the atoms and the molecules themselves. The intimate relation of the 

 fundamental charge with the atoms or groups of atoms, which play so 

 important a part in many chemical reactions, makes it appear probable 

 that in chemical reactions the negative electron is primarily concerned. 

 The horizon of chemistry is rapidly broadening in this direction, and a 

 study of electrolytic systems will unquestionably play a great part in 

 the ultimate elucidation of the mechanics of chemical reactions. 



6. The Ionic Theory. To account for the various phenomena which 

 have been observed in electrolytic solutions, the ionic theory has been 

 introduced. While ordinarily the ionic theory is supposed to include 

 fundamentally those concepts first introduced by Arrhenius, this theory 

 is, in fact, a composite theory in which many molecular mechanical 

 hypotheses are combined. It is to Arrhenius that is due the credit of 

 first having developed a theory of electrolytes, quantitative in its nature, 

 the correctness of which it was possible to determine by exact quantita- 

 tive methods. While the gaps left in the theory of electrolytic solutions 

 by the work of Arrhenius may not be overlooked, it should not be for- 

 gotten that up to the present time no other theory has been proposed 

 which is equally well able to account for so many and for so large a 

 variety of facts. 



The introduction of the theory of Arrhenius has, from the start, met 

 with the most determined opposition on the part of many chemists. It 

 is interesting, now, to note that in recent years the basis of the objections 

 to the theory of Arrhenius has greatly shifted and many of the originally 

 proposed objections have since been found to be without foundation. 



