October 23, 2020, 07:58:55 AM
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Topic: Soxhlet extractor - fluid changes consistancy?  (Read 207 times)

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Offline Zarius

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Soxhlet extractor - fluid changes consistancy?
« on: August 26, 2020, 08:00:44 PM »
So, I recently acquired a soxhlet extractor to help with my apothecary work, and I'm having an issue. I'm using ethyl alcohol as my solvent, and shredded spearmint as my extraction substance. As the system runs, it does exactly what I expect: The ethyl boils gently, evaporates, and then condenses with seemingly little to no loss in the upper chamber. Then the reliquefied, but hot, solvent soaks in the spearmint leaves, turning a deep, but transparent, shade of green as the chamber fills completely.

The problem comes once the solution peaks the gravity loop and drains back in to the base liquid. The compound turns a milky, opaque shade of green, then steadily turns a greyish-black over the span of the next several rounds.

I'm sure I'm just doing something wrong, but since this is my first time using any extraction process that involves actual lab equipment, I'm at a bit of a loss as to *what* I'm doing wrong.


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Re: Soxhlet extractor - fluid changes consistancy?
« Reply #1 on: September 01, 2020, 10:57:15 AM »

There is very little that you can do wrong with a Soxhlet extraction.

1. The solvent either boils, condenses and siphons or it does not—— yours does.
2. The solvent either extracts the desired compound(s) or it does not—-yours does.

As the Soxhlet cycles repeatedly, the extracted compound (s) remain in the heated ethanolic solution for some time.  I suspect that some chemical reaction is taking place to give you a precipitate that is largely insoluble in hot ethanol, and gives the milky appearance.

Can you use a different solvent e.g., CH2Cl2, C6H5CH3, hexane etc to extract the leaves?


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