EXCESS-ENTHALPIES IN THE BINARY-SYSTEMS WATER-HYDRAZINE, WATER-METHYLHYDRAZINE AND WATER-1,1-DIMETHYLHYDRAZINE - DETERMINATION AND MODELINGIN RELATION TO THE STRUCTURE OF THE LIQUID-PHASE

Excess enthalpies of the binary mixtures of water and hydrazine, N2H4 or methylhydrazine, CH3NHNH2 or 1,1-dimethylhydrazine, (CH3)2NNH2 are determined at 278.15 and 293.16 K. In the three cases, a chemical asso ciation model involving two hydrates (mono and tri- or tetrahydrate), a dimer for alkylhydrazine and assuming an ideal behavior of all speci es present, gives a good representation of the mixing properties of th ese mixtures.