benzyme said:
69ron said:
The only thing that matters is that you have enough solvent to fill the Soxhlet completely or it will never siphon.
it just needs to fill to the level of the top of the inner siphon, which (depending on the extractor) may be well below the top of the outer siphon
Exactly...and the amount varies according to how dense the plant material is. Actually I was a little incorrect in my statement. The general rule is like this:
Before starting the system, fill Soxhlet with cotton balls, add plant matter, cover with cotton balls. Add enough solvent to cause the Soxhlet to siphon once into the boiling flask. Then add solvent to fill the Soxhlet 1/2 way to the siphon point. For example, if it took 300 ml to cause a siphon, then add 150 ml more. That's the general rule anyway. It varies a little according to the solvent used. DCM, for example usually requires more solvent than IPA, or it won't siphon properly. If at any time it fails to siphon while the system is running, adding a little more solvent usually solves the problem.
There are cases when it won't siphon at all for many hours even after adding more solvent. This is usually because the drainage is inadequate (if the plant is too finely powdered and DE wasn’t added) and so it will just drip endlessly down from the Soxhlet’s siphon arm (the small tube) into the boiling flask. If this happens and the solvent level stays at the siphon arm, don’t worry, it is still extracting. It doesn’t actually need to siphon. As long as it is dripping back down, it is extracting.
But, if at any time the solvent level in the Soxhlet starts to reach the distillation arm (the larger tube) then you’re in trouble. This means the system is clogged. You should turn it off. Remove the plant material, replace any cotton with new cotton, and add DE to the material to prevent it from clogging again. Then put it back in the Soxhlet. This is almost never a problem if the plant material is coarsely ground, and often a problem if the plant material is very fine powder.
Remember if you are using very fine plant powder then add DE to it. This works really well to prevent clogging.