function state2 = getStateAfterIsochoricProcess(state1, state2, gas)
  if isfield(state1, "V")
    state2.V = state1.V ;
  end
  if isfield(state1, "v")
    state2.v = state1.v ;
  end
  equation.variableNames = [ "T" "p" "const"] ;
  equation.exponents     = [  1  -1    -1   ] ;
  variableName = getUnknownVariableNameFromConstEquation(state2, equation) ;
  state2 = updateStateFromConstEquation(variableName, state1, state2, equation) ;
end