  The dissolution process of small (initial (equivalent) radius $R_0 < 1$ mm)
long-chain alcohol (of various types) sessile droplets in water is studied,
disentangling diffusive and convective contributions. The latter can arise for
high solubilities of the alcohol, as the density of the alcohol-water mixture
is then considerably less as that of pure water, giving rise to buoyancy driven
convection. The convective flow around the droplets is measured, using
micro-particle image velocimetry ($\mu$PIV) and the schlieren technique. When
nondimensionalizing the system, we find a universal $Sh\sim Ra^{1/4}$ scaling
relation for all alcohols (of different solubilities) and all droplets in the
convective regime. Here Sh is the Sherwood number (dimensionless mass flux) and
Ra the Rayleigh number (dimensionless density difference between clean and
alcohol-saturated water). This scaling implies the scaling relation $\tau_c
\sim R^{5/4}$ of the convective dissolution time $\tau_c$, which is found to
agree with experimental data. We show that in the convective regime the plume
Reynolds number (the dimensionless velocity) of the detaching alcohol-saturated
plume follows $Re_p \sim Sc^{-1} Ra^{5/8}$, which is confirmed by the $\mu$PIV
data. Here, Sc is the Schmidt number. The convective regime exists when $Ra >
Ra_t$, where $Ra_t = 12$ is the transition Ra-number as extracted from the
data. For $Ra < Ra_t$ and smaller, convective transport is progressively
overtaken by diffusion and the above scaling relations break down.
