  The thermodynamic medium is treated as homogeneous phase equilibrium with a
special feature: the pressure of one phase is positive and the pressure of the
other is negative. From this point of view such medium is neither mixture,
usual solution nor gel (or sol as a whole) regardless its components (solvent
and dissolved substances). To base this statement the theoretical investigation
of the conditions of equilibrium and stability of the medium with
sign-alternative pressure is carried out under using the thermodynamic laws and
the Gibbs' equilibrium criterion. Thermal radiation and condensate are claimers
on the medium with alternating-sign pressure.
