I've gotten very good results with heptane, and a warm water bath vac purge (3x repeated). You could even dissolve the oil in a foodsafe alcohol (pure ethanol, acetone, isopropyl) so long as they are completely dry and pure, then evep and vac purge again.
Naptha has alot of different hydrocarbons in it, and heptane is a much refined version of naptha that evaps faster, and cleaner imho. As usual, always check your msds/do an evap test.
Just purge the hell out of it, and do an alcohol redissolve and another purge. Should get all but minute traces of the heptane out, and very low concentrations of alcohols that are not toxic in the doses that would be present as impurites that did not boil off.
Works just as well as butane without the danger of butane. I refuse to pressurize a vessel that is either metal and prone to electrostatic igniton, or a plastic that could shatter from temperature stress. Too many bad stories, and a few bad personal expirences in that dept.
You can also do a iso/etoh/acetone extraction first, and then do a hot water bath on that oil extracting with heptane. Will leave all the polar bad tasting crap behind and give you very good oil/wax if done correctly.
Supercritical gas extractions are sketchy enough, let alone supercritical highly flammable gases. CO2 mabey, but only with the right equipment (unfortunately is only viable on a larger commercial scale due to the mechanics of supercritical co2 extractions. Though it did produce the best wax i've ever tasted, co2 wax that is.
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