Dear Wolfram and others interested parties, Mizutani and Oana (1973, Separation of CO2 from SO2 ..., Mass Spectrometry, 21, 3, 255-258) published a method based on melting n-pentane. The melting point of n-pentane is -129 oC and it forms a slush. Melting points of other solvents were listed by Zhang in June, last year. See the isogeochem www site. However, we simply use ethanol and cool it with LN2 when we want to get rid of SO2 contamination. It becomes thick - like honey - below -100 oC and it is quite easy to keep -105 oC (it seems to be "stabilized" at that T). Best regards, Attila Dr. Attila Demeny Laboratory for Geochemical Research Hungarian Academy of Sciences Budapest, Budaorsi ut 45, H-1112, Hungary tel/fax: 36-1-319-3145 e-mail: [log in to unmask]