# The Thermodynamics of Chromatography - Interactions Between the Atoms of Hydrogen, Carbon, Chlorine and Bromine and an Exclusively Dispersive Stationary Phase > Experimental Data > Page 33

In figure 12
they are shown to have very similar slopes (0.402 and 0.406) and significantly
different intercepts (1.193 and 2.002). Comparing equations (19) and (20) it is
seen that each curve should exhibit the same intercepts, namely (_{})
but different slopes (_{}) and (_{}). The calculated
values of the intercepts are1.193 and 1.173, and the slopes are very different *vis*.
0.402 and 0.819.

**Figure
12 Graph of Log(Distribution Coefficient) against Number of Substituent Groups
in Methane**

The
distribution coefficients measured at different temperatures can be used to
identify the various thermodynamic parameters {*i.e*., (DG'_{H}), (DG'_{C}), (DG'_{Cl})
and (DG'_{Br})} with the aid of
a computer and a simple iterative program. Values for each parameter can be
taken over a wide numerical range and used in equations (2) to (11) to
calculate the log(K). Each calculated value can then be subtracted from that
obtained experimentally and the difference squared and summed for all the ten
equations. Each time the sum is reduced, the particular values of each
parameter are noted, and the process is continued until those values for the
parameters that provide the minimum sum of squares is obtained. The value of
each parameter calculated in this manner are given in table 2.