27 July 2011

Soxhelet Extractor

The first Soxhelet still was built in 1879 by Franz Von Soxhelet. Its main purpose is to extract soluble (lipids) from solids which would not be extractable through normal distillation methods. The main difference is that the solid is placed in a "thimble" which will then fill with condensed liquid from the solvent, which is being heated, below it.

Often used in chemistry for extracting fats, the Soxhelets purpose does not stop there. We have been experimenting with extracting flavour from wood for a few years as well as other solids we were unable to distill through normal means.

A simple breakdown of the process is.........

As the solvent is heated vapour will travel up the distillation arm and flood the section containing the solid material. The condenser will then cool the solvent after which it will drop back into the section housing the solid material.

The section containing the solid will slowly fill with the warm liquid from the vapour below. The idea is that some of the desired product, you are trying to extract, will then dissolve in the warm liquid. Once this section is full it is automatically emptied by a siphon. The liquid will then run back down into the base chamber and the process can be started all over again for as long as desired.

During each cycle some of the desired product will drip down into the bottom section, housing the solvent. After this has been done enough, or for a long enough period of time we are left with a very concentrated solvent.

Once the process is finished you can remove and concentrate the flavour by using a rotary evaporator, or through normal distillation methods.

Although not as quick and accurate as a Rotavapor The Soxhelet Extractor is a brilliant, and affordable alternative that means you can start experimenting with distilling your own ingredients. They are available through various science catalogs and easily found through google etc.

One word of warning though. Always be cautious of second hand stills as the may still contain residue from previous substances which may be poisonous to ingest.

1: Stirrer bar/anti-bumping granules 2: Still pot (extraction pot) - still pot should not be overfilled and the volume of solvent in the still pot should be 3 to 4 times the volume of the soxhlet chamber. 3: Distillation pat4: Soxhlet Thimble 5: Extraction solid (residue solid) 6: Syphon arm inlet 7: Syphon arm outlet 8: Reduction adapter 9: Condenser 10: Cooling water in 11: Cooling water out (image from wikipedia)

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