Abstract The two compounds (C 6 H 5) 2 Sn (CH 2) 4 and (C 6 H 5) 2 Sn (CH 2) 5 have been burnt in an aneroid combustion bomb and their vapour pressures measured by an effusion method. δfHm {(C6H5) 2Sn (CH2) 4, cr}=(195.0±5.2) kJ· mol− 1; δsubHm {(C6H5) 2Sn (CH2) 4,}=(106.8±5.5) kJ· mol− 1; δfHm {(C6H5) 2Sn (CH2) 5,}=(214.0±6.1) kJ· mol− 1; δvapHm {(C6H5) 2Sn (CH2) 5,}=(75.0. 0±1.5) kJ· mol− 1;