  Evaporation of multi-component liquid mixtures in confined geometries, such
as capillaries, is crucial in applications such as microfluidics, two-phase
cooling devices, and inkjet printing. Predicting the behaviour of such systems
becomes challenging because evaporation triggers complex spatio-temporal
changes in the composition of the mixture. These changes in composition, in
turn, affect evaporation. In the present work, we study the evaporation of
aqueous glycerol solutions contained as a liquid column in a capillary tube.
Experiments and direct numerical simulations show three evaporation regimes
characterised by different temporal evolutions of the normalised mass transfer
rate (or Sherwood number, $Sh$), namely $Sh (\tilde{t}) = 1$, $Sh \sim
1/\sqrt{\tilde{t}}$, and $Sh \sim \exp\left(-\tilde{t}\right)$. Here
$\tilde{t}$ is a normalised time. We present a simplistic analytical model
which shows that the evaporation dynamics can be expressed by the classical
relation $Sh = \exp \left( \tilde{t} \right) \mathrm{erfc} \left(
\sqrt{\tilde{t}}\right)$. For small and medium $\tilde{t}$, this expression
results in the first and second of the three observed scaling regimes,
respectively. This analytical model is formulated in the limit of pure
diffusion and when the penetration depth $\delta(t)$ of the diffusion front is
much smaller than the length $L(t)$ of the liquid column. When $\delta \approx
L$, finite length effects lead to $Sh \sim \exp\left(-\tilde{t}\right)$, i.e.
the third regime. Finally, we extend our analytical model to incorporate the
effect of advection and determine the conditions under which this effect is
important. Our results provide fundamental insight into the physics of
selective evaporation from a multi-component liquid column.
