Fig. 1 Psychrometer equilibration over 0.05 M (mol kg^-1) KCl salt standard solution. Each equilibration is modeled by a first-order equation (Eq. [1]), and fitted at 1-min intervals using nonlinear least squares analysis (solid lines). Equilibration times (t_eq) for measurements 1, 2, and 3 were 0.9, 2.7, and 10.0 min. The dashed lines represent ±0.05 MPa