Aerosols have been found to be protonated at levels consistent with pH values near zero, and specific sites may be expected to be even more acidic. Third, the proposed ring-closing reaction we observe could simply be an artifact of the unimolecular nature of this obseservation. This implies that dimer-forming reactions may occur in clusters of multiple organic acids or particle surfaces. This would significantly reduce the vapor pressure of acid molecules in those clusters or particles, leading to enhanced stability and growth rates. Finally, we note that the readily-achieved water loss from the cluster also facilitates an aging-related reduction in the O:C ratio of the cluster. Taken together, these observations speak to the complexity of the behavior of acidic clusters in the atmosphere.