An important aspect of any design exercise is the reliability of the e
mployed data. In the case of fixed-bed reactors, the inadequacies of t
he existing design information are now universally accepted. This cont
ribution presents an attempt to elucidate the dynamic dispersive featu
res of fixed beds by utilising a refined experimental approach togethe
r with a representative two-dimensional mathematical model of the phys
ical system. Manipulation of the predictions in comparison with the ob
served data provided best estimates of the effective axial and radial
dispersion coefficients for both the transient and steady-state situat
ions. Empirical expressions have been established for the a priori det
ermination of the dispersion terms. These are different from those pre
dicted by the literature correlations with the discrepancy becoming gr
eater with increasing values of Reynolds number. Values suitable for t
he transient case are found to be unsuitable for steady-state conditio
ns. Interactive effects between the axial and radial dispersion factor
s have also been established.