The isometric tensile stress generation observed when collagen fibers are immersed in aqueous solutions of lithium bromide ranging in molar concentration up to 7 was studied a t 23°C. The reverse process, namely, isomet,ric stress relaxation of the fiber occurring by subsequent immersion in distilled water, was also studied. We find that the data in the region of LiBr concentration up to about 2.5 moles/liter are adequately represented by a superposition integral where u(1) is the time-dependent stress generated by the collagen fiber held a t fixed length, c ( t ) is the history of LiBr molar concentration, and K ( t ) is the isometric contractility function, expressed as stress per unit salt concentration. We conclude that, within a limited range of salt concentrat,ion, a collagen fiber in a LiBr bath behaves as if it were a linear, time-invariant system defined mechanochemically by a single function K ( t ) which depends on the structural characteristics of the fiber while being independent of salt concentration. An analysis is presented of isometric mechanochemical data obtained under conditions of equilibrium by other workers who studied the behavior of collagen fibers in aqueous solutions either of urea, LiBr, or KCNS. The analysis shows that these independent (equilibrium) data confirm the linearity of the relation between isometric contractile stress and salt concentration on which our superposition integral representation is based. We also find that the asymptotic (infinite-time) value of the isometric stress is linearly related to the chemical potential of the salt as well, in agreement with the equilibrium thermodynamic treatment of mechanochemical processes by Katchalsky and Oplatka.