A method has been evolved for measuring the heats of combustion of spontaneously inflammable substances in the bomb calorimeter and applied to the following compounds: zinc dimethyl, zinc diethyl, zinc di-
n
-propyl, zinc di-
n
-butyl, cadmium dimethyl, boron trimethyl and aluminium trimethyl. The samples used were subjected to very thorough purification, revised melting points being given for cadmium dimethyl and aluminium trimethyl. The heats of formation, deduced by the application of additional thermal data, have been listed with all those so far determined for the metal alkyls, and the energies of dissociation and bond energies of the metal-carbon links estimated. This has entailed a recalculation of the heats of sublimation of aluminium and tin. From a comparison of the values obtained for the dissociation energies with evidence from spectroscopic and kinetic studies, a definite necessity for taking into account the energies required to promote the various elements to the states of maximum valency is apparent.
The strengths of certain covalent metal bonds
