From Wikipedia,
the free encyclopedia.
In
chemistry, saturation
has four different meanings:
- In
physical chemistry,
saturation is the point at which
a
solution of a substance can
dissolve no more of that
substance. This point, the
saturation point, depends on the
temperature of the liquid as
well as the chemical nature of
the substances involved. This
can be used in the process of
recrystallisation to purify
a chemical: it is dissolved to
the point of saturation in hot
solvent, then as the solvent
cools and the solubility
decreases, excess solute
precipitates. Impurities,
being present in much lower
concentration, do not saturate
the solvent and so remain
dissolved in the liquid. If a
change in conditions (e.g.
cooling) mean that the
concentration is actually higher
than the
saturation point, the
solution has become
supersaturated.
- In
physical chemistry when
refering to surface processes,
saturation denotes the degree of
which a surface is full of
something, e.g.
base saturation means the
fraction of
exchangeable cations that
are base cations. Similarly, in
soil chemistry soil moisture
saturation means that all voids
are filled with water and thus
all surfaces wetted, and
nitrogen saturation means
that an ecosystem, e.g. a soil,
can not store any more nitrogen
- In
organic chemistry,
saturation refers to an organic
compound having the maximum
amount of hydrogens possible:
i.e., no
double bonds or when every
carbon atom in a hydrocarbon
chain is attached to two
hydrogen atoms. Of simple
hydrocarbons,
alkanes are saturated, and
alkenes are unsaturated. In
the modern treatment of
electronic structure,
unsaturated compounds are
characterized by
pi electron systems. The
term is applied similarly to the
fatty acid constituents of
lipids, where the fat is
described as saturated or
unsaturated, depending on
whether the constituent fatty
acids contain carbon-carbon
double bonds. Unsaturated
is used when any carbon
structure contains double or
occasionally triple bonds. Many
vegetable oils contain fatty
acids with one (monounsaturated)
or more (polyunsaturated)
double bonds in them.
- In
biochemistry the term
saturation refers to the
fraction of total protein
binding sites that are
occupied at any given time.
