complete in any
ordinary solution. (2) The nature of the dissolved compound. At equal
concentrations substances differ much among themselves in the percentage
of dissociation. The great majority of salts are about equally
dissociated. Acids and bases, on the contrary, show great differences.
Some are freely dissociated, while others are dissociated to but a
slight extent.

~Strength of acids and bases.~ Since acid and basic properties are due to
hydrogen and hydroxyl ions respectively, the acid or base which will
produce the greatest percentage of these ions at a given concentration
must be regarded as the strongest representative of its class. The acids
and bases described in the foregoing paragraphs are all quite strong. In
10% solutions they are dissociated to about 50%, and this is also
approximately the extent to which most salts are dissociated at this
same concentration.

~Partial neutralization.~ 1. _Basic salts._ The chemical action
between an acid and a base is not always as complete as has
been represented in the foregoing paragraphs. For example, if
the base magnesium hydroxide (Mg(OH)_{2}) and hydrochloric acid
(HCl) are brought together in the ratio of an equal number of
molecules of each, there will be only half enough hydrogen ions
for the hydroxyl ions present.

Mg, (OH)_{2} + H, Cl = Mg, OH, Cl + H_{2}O.

Magnesium, hydroxyl, and chlorine ions are left at the close of
the reaction, and under the proper conditions unite to form
molecules of the compound Mg(OH)Cl. This compound, when
dissolved, can form hydroxyl ions and therefore possesses basic
properties; it can also form the ions of a salt (Mg and Cl),
and has properties characteristic of salts. Substances of this
kind are called _basic salts._

DEFINITION: _A basic salt is a substance which can give the
ions both of a base and of a salt when dissolved in water._

2. _Acid salts._ In a similar way, when sulphuric acid and
sodium hydroxide are brought together in the ratio of equal
numbers of the molecules of each, it is possible to have a
reaction expressed by the equation

Na, OH + H_{2}, SO_{4} = Na, H, SO_{4} + H_{2}O.

The ions remaining after all the hydroxyl ions have been used
up are those of an acid (H) and those of a salt (Na and
SO_{4}). These unite to form the substance NaHSO_{4}, and as
the s