  The coalescence of two liquid drops surrounded by a viscous gas is considered
in the framework of the conventional model. The problem is solved numerically
with particular attention to resolving the very initial stage of the process
which only recently has become accessible both experimentally and
computationally. A systematic study of the parameter space of practical
interest allows the influence of the governing parameters in the system to be
identified and the role of viscous gas to be determined. In particular, it is
shown that the viscosity of the gas suppresses the formation of toroidal bubble
predicted in some cases by early computations where the gas' dynamics was
neglected. Focussing computations on the very initial stages of coalescence and
considering the large parameter space allows us to examine the accuracy and
limits of applicability of various `scaling laws' proposed for different
`regimes' and, in doing so, reveal certain inconsistencies in recent works. A
comparison to experimental data shows that the conventional model is able to
reproduce many qualitative features of the initial stages of coalescence, such
as a collapse of calculations onto a `master curve' but, quantitatively,
overpredicts the observed speed of coalescence and there are no free parameters
to improve the fit. Finally, a phase diagram of parameter space, differing from
previously published ones, is used to illustrate the key findings.
