The combustion energies have been determined for the thirteen solid complexex of rare earth nitrates with glycine. The standard enthalpies of combustion, Δ c , ( c o o r ) H , and standard enthalpies of formation, Δ f , ( c o o r ) H , have been calculated for these complexes. The relationship of Δ f , ( c o o r ) H with the atomic numbers of the elements in the lanthanide series has been examined. The results show that a certain amount of covalency is present in the chemical bond between the rare earth cation and glycine.