Does anyone know the fractionation factor between CO2 and PbCO3 at 50C ? For anyone interested, PbCO3 reacts well in phosphoric acid at 50C and gives consistent results. Cheers Ian _______________________________________________________ Ian Cartwright Department of Earth Sciences Monash University Clayton, Vic 3168 AUSTRALIA Tel +61 (03) 9905 4887 / 4879 Fax +61 (03) 9905 4903 e-mail: [log in to unmask] May your peak tops be flat, may your isotopes be stable _______________________________________________________