To extrapolate the viscosity results for guaiacol-NO 3 shown in Fig. to other RH values and temperatures, we developed parameterizations that can describe the viscosities as a function of both RH and temperature, as done previously (see Section S5). For comparison, we have also extrapolated the guaiacol-OH SOA results from Kiland et al. to other RH values and temperatures. First, we fit a mole fraction-based Arrhenius mixing rule to the viscosity data in Fig. , resulting in a parameterization of viscosity as a function of RH at 294 K (dashed lines in Fig. ). Second, we extended the 294 K parameterization to higher and lower temperatures using the