# Dispersion in Chromatography Columns - Experimental Validation of the Van Deemter Equation > Page 90

Further by
substituting for (u_{opt.) }in
equation (65) it can be seen that the minimum plate height (H_{min}_{.)}
is given by,

(67)

Now, it is seen from equations (66) and (67) that the optimum linear velocity should be linearly related to the diffusivity of the solute in the mobile phase, whereas the minimum value of the HETP should be constant and independent of the solute diffusivity. This, of course, will only be true for solutes eluted at the same (k').

In table (1)
it is seen that the values of (k') and (k'_{e}) are approximately the
same for all the mobile phase mixtures employed and if it is assumed that the contribution
of the resistance to mass transfer in the stationary phase to (H) is
small, then equations (66) and (67) can be tested.

*J.Chromatogr*.,**270**(1983)64.

**Figure 23.
Graph of Minimum (H) against Solute Diffusivity**