  HD141569 is a pre-main sequence star with a disc uniquely placed between
protoplanetary and debris discs, similar to the older `hybrid' type discs. This
work aims to place the mass and spatial structure of the disc midplane in the
context of the debris, hybrid and protoplanetary discs. We observed HD~141569
with ALMA in 1.3~mm continuum and $^{13}$CO (2-1). This is the first detection
and image of the optically thin gas emission from the midplane of this disc. In
continuum emission, we detect a combination of an unresolved central peak and a
ring of millimetre emission at 220$\pm$10~au, slightly interior to one of the
rings discovered in scattered light. The minimum dust mass of the ring is
0.13$\pm$0.02~M$_{\oplus}$ while the unresolved millimetre peak at the stellar
location is predominantly thermal emission due to a minimum of
1.2$\pm$0.2~M$_{\oplus}$ of dust. $^{13}$CO is distributed asymmetrically
around the stellar position with a peak at 1.1" distance and a P.A. of
-33$^\circ$. The gas is detected as far as 220$\pm$10~au, a radial separation
the same as that of the mm ring. Assuming optically thin emission and standard
ISM abundances, we use our $^{13}$CO data to derive the gas mass in the disc of
(6.0$\pm$0.9) $\times 10^{-4}~$M$_\odot$. Comparison to published $^{12}$CO
data shows that $^{12}$CO is optically thick, explaining why estimates based on
$^{12}$CO underestimated the gas mass.
