Separation by Progressive Freezing

Component Separation by Progressive Freezing When the distribution coefficient is less than I, the first solid which ciystaUizes contains less solute than the liquid from which it was formed. As the frac tion which is frozen increases, the concentration of the impurity in the remaining liquid is increased and hence the concentration of impurity in the sohd phase increases (for k < 1). The concentration gradient is reversed for k > 1. Consequently, in the absence of diffusion in the solid phase a concentration gradient is estabhshed in the frozen ingot. 

A separation method involving use of -butyl alcohol (CAS no. [75-65-0](CH3)3COH, colorless liquid, b.p. 82.9°C, freezing point 25.5°C using 60% meta- and 40%p-cresol) has been also reported. Mixed cresols are added to 55.7% -butyl alcohol which forms an adduct having 70% p-cresol and 30% m-cresol. On progressive crystallization at 0°C and 10°C, the composition of 90% p-cresol, 10% m-cresol and also 95.5% p-cresol and 4.5% m-cresol is obtained. The Cbutyl alcohol is separated from p-cresol by distillation [15]. Here also more experimental work will be necessary to establish the commercial feasibility and economics of the process. 

The early sixties were golden times for the progress of investigation techniques in this field of science the first NMR studies in the anisotropic media of lyotropic liquid crystals [48] were done, the introduction of the freeze fraction technique for the preparation of electron microscopy probes (e.g., of cell membranes [49]) and the separation of different lyomesophases by centrifugation [47] were introduced all between 1960 and 1962. 

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