Studies of the states of water, hydrazine and hydrated hydrazine in ethylcellulose membrane were made for various mass fractions of solvents using differential scanning calorimetry (d.s.c.). Four or five energetically distinct states of these species in the membrane were identified and their quantitative estimations made. A new peak of enthalpy of mixing was identified at higher temperatures. Such a significant peak has not been previously recorded or discovered by d.s.c.