Enthalpies of a solution, at 298 K, of lithium perchlorate and Reichardt' dye were determined in diethyl ether (-26.0; 23), acetonitrile (-38.3, 10), acetone (-66.3; 0), dimethyl sulfoxide (-75.3; -16), tetrahydrofurane (-49.0, 7.5), nitromethane (-62.0; 0), ethyl acetate (-37.2; 13) and methanol (-51.9; -33 kJ mol(-1)), respectively. For lithium perchlorate, a sharp dependence on integral enthalpy of solution was observed in diethyl ether and nitromethane in the range of low concentration.