  The investigation of the processes of mineral deposit formation and their
history is a fundamental task. Solving this task can increase mining efficiency
and make a significant contribution to understanding the formation of the
Earth's crust. The main approach to solving this task is determining the values
of thermodynamic functions for phases present in deposits. One of the most
promising and flexible methods for studying thermodynamic properties is the EMF
method. This article describes the basic principles of the EMF method and
provides all possible interpretations of the obtained results. It has also been
demonstrated that direct EMF measurements can determine the composition of a
solid solution or alloy in a multicomponent system if its EMF dependencies are
known. Based on this fact, it can be concluded that any alloy or solid solution
in a multi-phase association, which undergoes composition changes with
temperature and can be quenched, can be used as a geothermometer or
geobarometer.
