With their Linear Theory of Thermochemical Equilibrium of Solids under Stress  and with later extensions, John Cahn and Francis Larché established a fundamental link between solid mechanics and the thermodynamics of multicomponent systems. Well in the 20th century each of the two fields was mature, and interactions between alloy chemistry and stress were acknowledged and understood in individual instances, yet it was only with the Larché-Cahn theory that a general joint description was presented. In view of the role of that theory as a key achievement of 20th century thermodynamics, it is amazing that little, if any, direct experimental demonstrations of its power have been reported. Arguably the most closely related phenomenon of experimental interest is the Gorsky effect, a transport of solute stimulated by cyclic applied stress. Internal friction experiments which exploit the Gorsky effect for measuring diffusion parameters have been of interest to the field of hydrogen diffusion in metals. Yet, the opportunities of probing the quasi-static elastic constants in open systems and of possibly even tuning the elastic response of materials based on the predictions by Larché and Cahn appear to have so far been largely overlooked. The talk will discuss experimental approaches that explore the ramifications of mobile solute on the elastic response of solids, confirming the impact of the Larché-Cahn theory for materials behavior.