well in a soxhlet you can use a very small amount of ethanol to extract a very large amount of bark. a 500mL soxhlet can fit 200-250g of bark and can extract with only 300mL of ethanol.

the soxhlet cycles fresh ethanol each time through reflux, its also quantitative. I usually run it over night so its equivalent of running 50-70 times fresh solvent through the bark.

outside of this you will probably only do 3-4 extraction cycles, and more solvent is necessary, i start with at least twice the volume to the bark.

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for a/b i just reflux the tar in dilute HCl, or acetic acid with strong stirring. Sometimes it can be a bit tough to break up. Alcohol can also extract a lot of coloured components, so I usually defat too before basifying. This is my general technique not limited to MHRB