Thermochemistry has been closely associated with techniques such as reaction￾solution and combustion calorimetry, although it has long been recognized that
thermochemical information can also be obtained from noncalorimetric methods,
such as equilibrium and kinetics experiments.
Historically, some of those approaches have been developed with a consid￾erable degree of independence, leading to a proliferation of thermochemical
concepts and conventions that may be difficult to grasp. Moreover, the past
decades have witnessed the development of new experimental methods, in
solution and in the gas phase, that have allowed the thermochemical study of
neutral and ionic molecular species not amenable to the classic calorimetric and
noncalorimetric techniques. Thus, even the expert reader (e.g., someone who
works on thermochemistry or chemical kinetics) is often challenged by the variety
of new and sophisticated methods that have enriched the literature. For example,
it is not uncommon for a calorimetrist to have no idea about the reliability of
mass spectrometry data quoted from a paper; many gas-phase kineticists ignore
the impact that photoacoustic calorimetry results may have in their own field;
most experimentalists are notoriously unaware of the importance of computa￾tional chemistry; computational chemists often compare their results with less
reliable experimental values; and the “consistency” of thermochemical data is
a frequently ignored issue and responsible for many inaccuracies in literature
values.