Shown in Fig. (solid line) is the calculated mixing times as a function of temperature of CO2 within a 200 μm particle (roughly the diameter of the supermicron particles observed using optical microscopy, which are the conglomerate of smaller aerosol particles). At temperatures of 36 and 52 °C, the mixing times of CO2 within 200 μm catechol SOA particles are 39600 and ~3640 s (11 and 1 h), respectively. Recall that these mixing times are based on a lower limit estimate of the viscosity of catechol at room temperature, so the mixing times here are also lower limits. The calculated mixing is relatively slow and these mixing times are longer than the experimental times used in the optical microscope experiments (Fig. and). Hence, any CO2 or acetone produced within a 200 μm particle during heating will not immediately escape the particles and could lead to the observed boiling behavior (see below).