A number of reactions pertaining to the heat of formation of aluminium acetylacetonate have been measured in 50%(by vol.) dioxan–water solution, and enthalpy changes for the following processes (A = acetylacetonate) have been obtained. AlCl3(solv.)+ 3NaA (solv.)= AlA3(solv.)+ 3NaCl (solv)ΔH=–3·894 kcal./mole, Al (g)+ 3HA(enol)(g)= AlA3(g)+ 3/2 H2(g)ΔHchel.=–239·97 kcal./mole, Al (c)+ 15C (c)+ 10·5H2(g)+ 3O2(g)= Al(C5H7O2)3(c)ΔHf°=–427·59 kcal./mole, Al (g)+ 3C5H7O2·(g)= Al(C5H7O2)3(g)ΔH=–398·85 kcal./mole From the heat of formation of aluminium acetylacetonate in the vapour state, the aluminium–oxygen bond energy is derived; D(Al–O) at 25°= 66 kcal./mole.