  We consider a binary mixture of chemically active particles, that produce or
consume solute molecules, and that interact with each other through the
long-range concentrations fields they generate. We analytically calculate the
effective phoretic mobility of these particles when the mixture is submitted to
a constant, external concentration gradient, at leading order in the overall
concentration. Relying on a analogy with the modeling of strong electrolytes,
we show that the effective phoretic mobility decays with the square-root of the
concentration: our result is therefore a nonequilibrium counterpart to the
celebrated Kohlrausch and Debye-H\"uckel-Onsager conductivity laws for
electrolytes, which are extended here to particles with long-range
nonreciprocal interactions. The effective mobility law we derive reveals the
existence of a regime of maximal mobility, and could find applications in the
description of nanoscale transport phenomena in living cells.
