AT THE END of the 19th century, the most pressing question in theoretical chemistry
was the determination of what was termed “chemical affinity,” whether a given
combination of chemicals might react. Would all the reactants be transformed
into products, or would the reaction reach equilibrium? Could the equilibrium
be predicted?
The laws of thermodynamics seemed to offer the most promising approach to
a solution of the problem. Stated as a chemist at the time would understand them,
the first law of thermodynamics required that energy, as represented by the sum
of a closed system’s heat and any external work done by the system, is conserved,