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

Abstract

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.