Static magnetic field effect in the framework of the radial pair mechanism (RPM) theory was studied oil the biologically significant chemical reaction between ascorbic acid and Fremy's salt. The data indicate that the reaction rate depends on the applied magnetic field strength. The time scale of the studied reaction and the improved continuous-wave electron paramagnetic resonance system allowed for the first time the direct comparison of the amplitude differences between exposed and control samples in the strictly same boundary conditions. Until now the RPM was Studied in a different time scale, focusing only on faster reactions by time-resolved techniques or by spectrophotometer measurement. The magnetic field effects presently measured call not be extended tout Court to living systems; however the understanding of magnetic field sensitivity in basic chemical reaction ill Vitro Could help clarifying the underlying basic step of interaction between magnetic fields and biological systems,: