6o2 
CHEMISTRY: W. D. HARKINS 
Proc. N. a. S. 
hypothesis that such salts are collections of polar atoms, which are often 
called ions. 
Let us suppose that in the gaseous state in a system there are sodium 
atoms in combination with chlorine atoms. These pairs are molecules, 
since, on account of their considerable relative distance from other 
particles, their electromagnetic fields are largely self contained. It is 
probable that if such molecules remain at temperatures at which the solid 
salt exists, the distance of the sodium from the chlorine atom, will not be 
very different from the similar distance in the solid state. On the basis 
of the nomenclature which considers that the solid salt consists of ions 
alone, it might be said that the gaseous molecule is also ionized (called 
intra-molecular ionization by Thomson), but still remains together as a 
single molecular particle, though it seems preferable to use the terms 
presented by Lewis and Bray, and consider the molecule as polar, and as 
made up of polar atoms. If many of these gas molecules pass into an 
aqueous system, then it is probable that the polar atoms in practically 
all of them, will separate to greater distances than that between unlike 
atoms in the gaseous molecules. In any event the sodium chloride 
particles would not persist as molecules, since their electromagnetic fields 
would interact with those of the solvent (this action is commonly known 
as hydration or solvation). If the terminology is such that the salt is 
considered as 100% ionized in the solid or gaseous state, then it would 
be absurd to say that it is less than totally ionized in solution. However, 
many of the pairs of positive and negative polar particles, are so close 
together that they are not free to move in the electric field, and so in the 
accepted sense of the term, there are un-ionized or non-ionized aggregates. 
On the basis of the complete ionization convention these may be called 
hound, and those which are far apart, free ions. 
From this standpoint let us consider that there exist at any instant 
in the solution, all degrees of firmness of binding, from ions which are 
far apart and almost entirely free, down to those which are most closely 
bound, and therefore are not ions in the accepted sense. Suppose that 
the problem is assigned of determining the degree of separation or of 
dissociation of the electrolyte. It is obvious that according to the way 
in which the distinction is drawn between the dissociated and undisso- 
ciated fractions, the calculated results will differ. 
In order to prevent a confusion in terms in my own class work I have, 
for the past seven years used the expression, highly ionized salts, acids, 
and bases, are completely ionized or polarized in aqueous solution, but 
what may be considered the mean degree of separation or of dissociation, 
depends upon the method by which it is determined, since it is not to 
be expected that different measuring devices will draw the line of dis- 
tinction at exactly the same place. 
