Mass spectrometric studies at high temperatures. Part 24.—Thermodynamics of vaporization of SnF2and PbF2and the Dissociation energies of SnF and PbF

Vapour species in the SnF2, SnF2+ Sn, CaF2+ Sn and PbF2 systems have been studied mass spectrometrically. The presence of dimers and trimers as well as monomers of SnF2 was noted and the average SnF2—SnF2 bond energy for these polymers was 20.0±2 kcal mole–1. PbF2 does not dimerize but disproportionates into Pb + PbF4, and a value of 382±2 kcal mole–1 was measured for the heat of atomization of PbF4. The dissociation energies of PbF and SnF were 85±2 and 111.5±3 kcal mole–1 respectively.