  Density is one of the most important properties of seawater and is used in
various marine research and technology. Traditionally, in the practice of
oceanographic research, it is customary to con-sider density as a dependent
parameter, which is a function of several other parameters taken as
independent. Usually the following three parameters are used as the independent
parameters: temperature, hydrostatic pressure and salinity. The issues of
temperature and hydrostatic pressure measuring in situ are technologically well
developed, while in the salinity measuring there are still unsolved problems.
This is due to the fact that salinity is such a property that it is simply
impossi-ble to determine directly in situ. To eliminate the problems associated
with measurements of sa-linity, the authors developed the special new kind
equation. That equation of the new kind ex-press the density of sea water
through independent and in situ measured parameters: temperature, hydrostatic
pressure and sound speed. The novelty of this approach is that using of the
sound speed as the independent parameter makes it possible to exclude
measurements of salinity. The authors developed two such new equations for the
different cases of using. The first new equa-tion is intended for use in
technical applications and reproduces the sea water density in a wide range of
the aquatic environment parameters with a root mean square deviation of 0.062
kg/m3. The second more precise new equation is intended for scientific
applications and reproduces the sea water density in a narrower oceanographic
range of parameters with a root mean square devi-ation of 0.0018 kg/m3.
