Solvent extraction 353 slope is generally always unity. However, as the solute becomes more concentrated, there may be a tendency for solute molecules to associate with each other in one of the phases. Thus, the equilibrium data in Fig. 6 suggest that the phenol molecules form a dimer in the organic phase, probably by hydrogen bonding, leading to a slope of 2 in the distribution plot The possibility of complex formation in one of the phases illustrates concern that many industrial extraction processes involve not only physical transfer of molecules across an interface but, also, that there may be a sequence of chemical steps which have to occur before the physical transfer can take place, and which may be rate limiting Limin L imati Figure 6. Distribution of phenol between water and chlorinated methanes Whenever the distribution coefficient is greatly different than unity thereis an implication that there exists an affinity of the solute for that specific solvent, and this affinity may involve some loose chemical bonding Examples of computer programs for predicting and correlating equi librium data are described by Lo, Baird, and Hanson. [2Solvent Extraction 353 slope is generally always unity. However, as the solute becomes more concentrated, there may be a tendency for solute molecules to associate with each other in one of the phases. Thus, the equilibrium data in Fig. 6 suggest that the phenol molecules form a dimer in the organic phase, probably by hydrogen bonding, leading to a slope of 2 in the distribution plot. The possibility of complex formation in one of the phases illustrates the concern that many industrial extraction processes involve not only the physical transfer of molecules across an interface but, also, that there may be a sequence of chemical steps which have to occur before the physical transfer can take place, and which may be rate limiting. I IO' Y 8 phenol gorganlc 10-1 10- g phenol IO" 8 ualrr Figure 6. Distribution of phenol between water and chlorinated methanes. Whenever the distribution coefficient is greatly different than unity, there is an implication that there exists an uflnity ofthe solute for that specific solvent, and this affinity may involve some loose chemical bonding. Examples of computer programs for predicting and correlating equi￾librium data are described by Lo, Baird, and Hamon.[*]