  The third law of thermodynamics has been verified experimentally, but how to
perfectly express such a law in theory has become a cross-century problematic
issue. It is found from the recent researches that by introducing an innovative
method, the Nernst equation can be obtained directly from the experimental data
of chemical reactions at low temperatures without the need for artificial
additional assumptions appearing in textbooks, so that the Nernst theorem
should be replaced by the Nernst statement. The heat capacity statement
proposed recently can be also obtained from the experimental data of the heat
capacity at low temperatures. The heat capacity statement and the Nernst
statement are proved to be mutually derivable and the two are equivalent. The
unattainability statement of absolute zero temperature is only a coloration of
the Nernst statement or the heat capacity statement. Simultaneously, the
defects and deficiencies related to the contents of the third law of
thermodynamics appearing in textbooks are pointed out and corrected. The
results obtained show clearly that the Nernst theorem and the unattainability
statement of absolute zero temperature should be withdrawn from the statements
of the third law of thermodynamics. It is important to find that the Nernst
statement and the heat capacity statement are two equivalent statements of the
third law of thermodynamics, which can solve the centennial debate problems of
the third law of thermodynamics and supply the perfect statements for the third
law of thermodynamics.
