The kinetics of thermal dehydration of K 2x/3 Cu [Fe(CN) 6 ] 2/3 ÁnH 2 O was studied using thermogravimetry for x = 0.0 and 1.0. Data from both non-isothermal and isothermal measurements were used for model-free kinetic analysis by the Friedman and KAS methods. The water content was determined to be n = 2.9-3.9, plus an additional *10% of water, likely surface adsorbed, that leaves very fast when samples are exposed to a dry atmosphere. The determined average activation energy for 0.2 B a B 0.8 is 56 kJ mol -1 . The dehydration is adequately described as a diffusion-controlled single-step reaction following the D3 Jander model. The determined dehydration enthalpy is 11 kJ (mol H 2 O) -1 for x = 0.0 and 27 kJ (mol H 2 O) -1 for x = 1.0, relative to that of water. The increase with increasing x is evidence that the H 2 O molecules form bonds to the incorporated K ? ions.