LIQUID-SOLID PHASE-TRANSFORMATION OF A 2-COMPONENT SYSTEM (1,2-1,4 CHLORONITROBENZENES) HELD INSIDE POROUS MATERIALS

The liquid-solid phase changes of a perfect solution (1,2-1,4 chloroni trobenzenes) held inside porous materials of known textural characteri stics have been studied by using a DSC technique. When the pores are s aturated with the condensate, the successive steps of equilibrium crys tallization depend on whether the porous volume can be filled or not w ith the eutectic liquid. By varying the amount and initial composition of the solution used, the composition of the condensate which crystal lizes inside the biggest pores of a given porous material, can be adju sted. By measuring the corresponding temperature, it is then possible to determine the phase diagram of the binary system in a given state o f division. The equilibrium curves are similar to those of bulk binary systems for the two considered states of division. They are all the m ore shifted towards lower temperatures as the capillary condensate is more finely divided. The temperature shift depends on the composition, like the ratio of the solution-crystal 1,2 (or 1,4) interfacial tensi on to the partial volumic entropy of transition of the 1,2 (respective ly 1,4) component.