5
vacuum on itself. If temperatures will not allow this negative pressure, the pump will always be fighting this
opposing pressure.
If you refer to (fig. 1), you can see that solvent pressure is directly related to its temperature. As the solvent
increases in temperature above the boiling point (
fig.2),
pressure will increase. Alternatively, since we are
working in a system that is at a full vacuum, as the solvent gets colder than the boiling point, pressures will
start to go into the negative.
When distilling the solvent in the collection, it is important to note the boiling point of the most delicate
compound in your extract
;
i.e. when extracting hops or rosemary, your recovery temperature should not exceed the
boiling point of your lowest boiling terpene, Beta-caryophyllene. It is important to note that boiling points decrease as
the level of vacuum increases. The change in boiling points can be calculated using the Clausius Clapeyron Equation. For
B-caryophyllene,
▪
[
246.2°F @760torr (-0.00in.hg) 0% vac]
▪
[180.00°F @100torr (-25.98 in.hg) 87% vac]
▪
[159.99°F @50torr. (-27.95 in.hg) 93.5% vac]
▪
[138.82°F @23.4torr (-29 in.hg) 96.9% vac]
▪
[109.44°F @7.6torr. (-29.62 in.hg) 99% vac]
By keeping the warm water bath below the boiling point of the lowest boiling compound, you are able to
preserve the full spectrum of your extract.
Solvent
Boiling
Point
n-Butane (R-600)
30.2
°
F
(-1
°
C)
Isobutane (R-600a)
10.94
°
F
(-11.7
°
C)
F
IG
.
1
F
IG
.
2
