The effect of gas condensation during the isothermal decompression.
The effect is counter-intuitive as most practical fluids experience decrease in density under isothermal decompression.
The most popular practical example of Retrograde Condensation behaviour is Natural Gas with initial temperature higher than pseudo-critical but lower than Cricondentherm.
See also
Natural Science / Physics / Thermodynamics / Thermodynamic system / Phase / Phase transition
[ Condensation ][ Vaporization ]