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226 CHAPTER 3

Such ionic crystals are known as true electrolytes or ionophores (the Greek suffix
phore means “bearer of”; thus, an ionophore is a “substance that bears ions”). When
a true electrolyte is melted, its ionic lattice is dismantled and the pure liquid true
electrolyte shows considerable ionic conduction (Chapter 2). Thus, the characteristic
of a true electrolyte is that in the pure liquid form it is an ionic conductor. All salts
belong to this class. Sodium chloride therefore is a typical true electrolyte.

3.2.2. Potential Electrolytes: Nonionic Substances that React with the
Solvent to Yield Ions
A large number of substances (e.g., organic acids) show little conductivity in the
pure liquid state. Evidently there must be some fundamental difference in structure
between organic acids and inorganic salts, and this difference is responsible for the
fact that one pure liquid (the true electrolyte) is an ionic conductor and the other is not.
What is this difference between, say, sodium chloride and acetic acid? Electron
diffraction studies furnish an answer. They show that gaseous acetic acid consists of
separate, neutral molecules and the bonding of the atoms inside these molecules is
essentially nonionic. These neutral molecules retain their identity and separate exist-
ence when the gas condenses to give liquid acetic acid. Hence, there are hardly any
ions in liquid acetic acid and therefore little conductivity.
Now, the first requirement of an electrolyte is that it should give rise to a
conducting solution. From this point of view, it appears that acetic acid will never
answer the requirements of an electrolyte; it is nonionic. When, however, acetic acid
is dissolved in water, an interesting phenomenon occurs: ions are produced, and
therefore the solutions conduct electricity. Thus, acetic acid, too, is a type of electro-
lyte; it is not a true electrolyte, but a potential one (“one which can, but has not yet,
become”). Potential electrolytes are also called ionogens, i.e., “ion producers.”
How does acetic acid, which does not consist of ions in the pure liquid state,
generate ions when dissolved in water? In short, how do potential electrolytes work?
Obviously, there must be some reaction between neutral acetic acid molecules and
water, and this reaction must lead to the splitting of the acetic acid molecules into
charged fragments, or ions.
A simple picture is as follows. Suppose that an acetic acid molecule collides with
a water molecule and in the process the H of the acetic acid OH group is transferred
from the oxygen atom of the OH to the oxygen atom of the A proton has been
transferred from to