The message
from "Brian Sharrock" contains these words:

'Tight' control loop systems _might_ achieve 78.4 deg but it'll
be 78.4 +/- a 'bit'. Roughly; the size, and direction, of 'a bit' is going
to become more expensive the smaller 'a 'bit' is.

And anyway, 78.4°C is only the standard boiling point. If the air
pressure isn't 1Bar that day then it'll wander anyway.

I'd make a bain-marie and warm that gently - the fractions will come off
one by one anyway provided the temperature's raised gradually enough. A
large mass of water in the outer jacket will make this easier.

--
Skipweasel
Pay no attention to that man behind the curtain.