The definitions of the affinity tensor and the tensor of chemical potential of an immobile component of a solid are given. The mechanochemistry of a liquid is formulated. Mechanically anisotropic states of a solid and their influence on affinity are analyzed. Thermodynamic equations are deduced relating the chemical potential tensor to the stress and strain tensors. The mechanochemistry of an ideally elastic solid and of a solid with mobile components, as well as the mechanochemistry of an interface, are formulated. As an example, the mechanochemical effect of dissolution (evaporation) is considered including its dependence on the deformation sign.