RETARDED SOLID-STATE REACTIONS .3.

Solid state reactions and reconstructive phase transitions exhibit mor e or less a large hysteresis between reaction temperatures taken from DTA-heating and -cooling curves. For ternary lanthanide chlorides the equilibrium temperatures could be obtained by e.m.f-measurements in ga lvanic chlorine cells for solid electrolytes using A(+)-ion (A=alkalin e metal) conducting diaphragms. By quenching, high-temperature phases can often be transformed to metastable room-temperature phases. In thi s case the equilibrium state must be established by annealing at suffi ciently high temperature, or it must be tried to synthesize the compou nd in its stability range from suitable precursor systems.