Apparent violation of thermodynamics second law under Van der Waals gas   expansion in vacuum
  Examining textbooks of thermodynamics we have not able to find a proof of increasing of entropy under free adiabatic expansion in vacuum based on the state equation of the Van der Waals gas. This communication remedies the situation. During proving we faced with an amusing example of apparent violation of thermodynamics second law. 
Yury A. Koksharov