HOMOGENEOUS NUCLEATION OF VAPORS - CRITICAL SUPERSATURATION MEASUREMENTS FOR METHANOL, ETHANOL, 1-PROPANOL, AND 2-PROPANOL

We report data describing the temperature dependence of the critical s upersaturation for methanol, ethanol, 1-propanol, and 2-propanol. The data obtained in this investigation came from two different thermal di ffusion cloud chambers. A few data points were also included for compa rison purposes from a literature report involving a third thermal diff usion cloud chamber (ref 22). Together, these data span temperature ra nges of 150-160 K. The critical supersaturation data were obtained usi ng either helium or hydrogen as the background gas. On the basis of ou r observations for the temperature ranges and the total pressure (1.01 3 bar) employed in this investigation, we find that the critical super saturations for all of these alcohols when hydrogen is used as a backg round gas are either equal to or greater than those obtained when heli um is used as the background gas. This behavior is consistent with obs ervations reported in refs 18 and 23 resulting from studies in which t he dependence of the critical supersaturation of these alcohols on the background gas was investigated and in which the critical supersatura tion was found to depend on both the kind of background gas as well as the total pressure.