The
physical properties of seawater vary with the concentration of the
dissolved constituents. A convenient parameter for describing the
composition of seawater is the salinity, *S*, which is defined
in terms of the electrical conductivity of the seawater sample:
where *K*
is the ratio of the conductivity of the seawater sample at 15^{o}C
and normal atmospheric pressure to the conductivity of a potassium
chloride solution in which the mass fraction of KCl is 0.0324356, at
the same temperature and pressure, and the values of the
coefficients are:
Thus when
*K*=1, *S*=35 exactly. Here we see the practical side of
the above salinity definition: the value of *S* is roughly
equal with the mass of dissolved compounds, expressed in grams per
kilogram of seawater, while the definition in terms of electrical
conductivity allows meaningful measurements. Salinity values in the
open oceans at mid latitudes typically fall between 34 and 36. |