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energy of distribution can be allotted to different parts of a molecule and, thus, their contribution  to solute retention can be disclosed. In addition, from the relative values of the standard enthalpy and standard entropy of each portion or group, the manner in which the different groups interact with the stationary phase may also be revealed. Another interesting relationship arises from the above treatment and that is the standard entropy term tends to increase with the standard enthalpy term. This relationship between entropy and enthalpy has been reported many times in the literature. An example of a graph relating (DHo) to (DSo), produced by Martire and his group (K), is shown in figure 11. From a theoretical point of view, this relationship between standard enthalpy and standard entropy is to be expected. Any increase in enthalpy indicates that more energy is used up in the association of the solute molecule with the molecules of the stationary phase.   &

nbsp; The linear relationship between the standard enthalpy and standard entropy indicates that, if either the standard enthalpy or standard entropy was known, the other can be calculated. It is also shown that there is a linear relationship between the atomic polarizability of the interacting atom and its standard enthalpy of interaction. Thus, there is also the possibility of calculating the standard enthalpy, hence the standard entropy and thus the retention of a solute, from its molecular structure and the physical and electrical properties of it component atoms. However, at this time, there appears to be a relatively large contribution to the standard enthalpy of interaction that is independent of the polarizability of the interacting atom. This may be due to some other physical characteristic of the distribution system that contributes to the standard enthalpy. Alternatively, the

nbsp;   Figure 14 Graph of Standard Entropy against Standard Enthalpy for Each Element A negative value or (DHo) means that heat is evolved when interaction takes place in the stationary phase as a result of the forces between the atom and the n-octadecane. From table 3 it is seen that the standard entropy term increases with the standard enthalpy term. This relationship between standard entropy and standard enthalpy  is shown in figure 14.      It is seen that there is an impressive clean linear correlation between (DHo) and (DSo) (index of determination 1.000). The excellent correlation is due to the condition that only one interactive process is significantly active in the distribution (i.e., dispersive interactions). As already discussed, a linear relationship between standard enthalpy and standard entropy is to be expected. An increase in enthalpy indicates that more

nbsp; Figure 10. Graph of Intercept and Slope from [Log(V'r(T))/Number of CH2 Groups Curves] for a Series of 1-Chlorohydrocarbons 1/T   The difference between the methyl group, methylene group, and the chlorine atom is quite striking. The enthalpy and entropy values for the methylene group are again very close to those obtained from the n-alkane series. As would be expected, the chlorine atom has both a higher enthalpy term and a higher entropy term than the methylene group. The high enthalpy contribution probably arises from its larger mass and size which would be expected to provide stronger interactions with the stationary phase molecules. Its increased entropy contribution arises from it being a terminal atom as opposed to a group, consequently, prior to interaction with the stationary phase, it has much greater freedom. Th  e contribution of the methylene group and the chlorine atom can be calculated from the enthalpy and entropy values given in figure 10 (cf

nbsp;                 standard enthalpy,             (j) is the proportionality constant relating polarizability to                   standard enthalpy,       and (x) is that part of the standard enthalpy that is independent of                  the polarizability of the

Thus,                            DGo = DHo - TDSo                                 (2)     where (DHo) is the standard enthalpy,     and (DSo) is the standard entropy. The standard enthalpy and standard entropy represent two distinctly different portions of the energy associated with distribution and are related to quite different parts of the distribution processes.   The enthalpy term represents the energy involved when the solute molecules break their interactions with the mobile phase and interact with, and enter, the stationary phase. These interactions