We contribute to the development of steady state thermodynamics for isothermal and homogeneous chemical systems, through a generalized Einstein fluctuation relation, by utilizing a local steady state interpretation of static concentration fluctuations of reaction intermediates. For systems of constrained total chemical affinity the ‘‘next-particle ratio’’ of the probability density, q=P(N+1)/P(N), derived from a usual chemical master equation is employed for the construction of chemical potential steady state laws. This analysis is based on the identification of the exponent of the distribution, as a generalized availability of local fluctuations. Further, pressure steady state laws are derived through a generalized Gibbs–Duhem equation, restricted to constant ‘‘disequilibrium variables.’’ Such variables are introduced as state variables, in addition to the classic ones, for the characterization of steady states. They relate to externally controlled generalized forces or affinities, which induce the flows of mass through the system. Within the local steady state approach, the state laws enable the construction of the generalized availability, as state function for quasisteady state processes beginning from a reference state. This quantity is found to provide a Liapounov function for the deterministic evolution of the system towards stationary states in analogy to a previously developed local equilibrium theory. The analysis is applied to two-variable chemical systems of high stoichiometry change, but should be capable of extension to general hydrodynamic systems.