  Macroscopic nonextensive thermodynamics is studied without recourse to
microscopic statistical mechanics. It is shown that if entropy is nonextensive,
the concept of physical temperature introduced through the generalized zeroth
law of thermodynamics necessarily leads to modifications of the first law of
thermodynamics and some of thermodynamic relations including Clausius
definition of thermodynamic entropy. It is also shown, by applying this
generalized Clausius entropy to a composite nonextensive system, how the
nonextensive entropy and the quantity of heat consistently behave in an
arbitrary thermodynamic process. An important point emerging from this is that
the entropy coefficient, which connects the microscopic and macroscopic
concepts, cannot be removed from the macroscopic nonextensive theory. This fact
suggests that nonextensivity may require atomism for macroscopic thermodynamics
at a logical level.
