From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Newsgroups: sci.chem
Subject: Re: [Q] What is "soxhelt"?
Date: Fri, 04 Sep 1998 20:39:12 GMT

mike crimmins <mpc584@world.std.com> wrote:

>Perhaps you mean soxlet extraction.  It was an ancient method of
>extraction. Check some old books like previous to 1988.

We use Soxhlet extraction almost on a daily basis, and it's
still the standard method for determining the fat content of
various natural products - especially foods and oils seeds.
So it's actually detailed in most modern relevant standard
methods as well. The two best sources would be the AOAC
Official Methods of analysis, and the Americam Oil Chemists'
analytical methods, although I suspect the ASTM and ISO
may also have soxhlet methods.

>> I wonder what soxhelt is.

So do I. Try searching on Soxhlet instead.

>> Give me an infromation.

Use a library, and learn to say please when asking others
to do somthing for your benefit. I'll include an
illustration below from an old post of mine, however
the answer to your question was in the sci.chem FAQ,
and you should have looked there first.

>> And, How can the fat be determined using soxhelt?

[ From the sci.chem FAQ ]

16.6  What does a Soxhlet extractor do?

The soxhlet extractor enables solids to be extracted with fresh warm solvent
that does not contain the extract. This can dramatically increase the
extraction rate, as the sample is contacting fresh warm solvent. The sample
is placed inside a cellulose or ceramic thimble and placed in the extractor.
The extractor is connected to a flask containing the extraction solvent, and
a condenser is connected above the extractor. The solvent is boiled, and the
standard extractor has a bypass arm that the vapour passes through to reach
the condenser, where it condenses and drips onto the sample in the thimble.
Once the solvent reaches the top of the siphon arm, the solvent and extract
are siphoned back into the lower flask. The solvent reboils, and the cycle
is repeated until the sample is completely extracted, and the extract is
in the lower flask.

There is an alternative design where the hot solvent vapour passes around
the thimble, thus boiling the solvent in the thimble - this can be a problem
if low-boiling azeotropes form. Procedures for using soxhlet extractors are
described ( along with illustrations which might make the above description
comprehensible :-) ), in Vogel and many other introductory organic laboratory
texts.

[ End Extract ]

         Warm Solvent               Hot Solvent
          Extractor                  Extractor
        ( most common )            ( less common )

            | |                         | |
           /| |\                       /| |\
           || | =                      || | = Water Out
           || ||         Condensor     || ||
           || ||                       || ||
Water In  = | ||                      = | ||
           \| |/                       \| |/
            | |                         | |
           \\ //                       \\ //
           /   \          Adaptor      /   \
          /     \                     /     \
         \\     //                   \\     //
         _|     |                    |       |
        /_      |  __                |       |  __
       // |     | |  |               |       | |  | Siphon
       || |     | ||||               ||     || ||||  Arm
Vapour || ||xxx|| ||||  Thimble      |||xxx||| ||||
Arm    || ||xxx|| ||||               |||xxx||| ||||
       || ||xxx|| ||||  x=Feed       |||xxx||| ||||
       || ||xxx|| ||||               |||xxx||| ||||
       || ||xxx|| ||||               |||xxx||| ||||
       || | \_/ |_|||/               | \\_//_|_||||
       || |________||                |  \_______||/
       || |     |  || Solvent        |       |  ||
       || |   __|__|| Liquid         |    ___|__||
       || |  / _____/ Return         |  / _______/
       ||_|  || |                    |  ||   |
       |__      |                     \     /
          \    /                       \   /
          \\  //                       \\ //
           |  |                        |   |
           |  |    Boiling Flask       |   |
          /    \                      /     \
        /        \                  /         \
      /___________ \              /             \
     |  Solvent +   |            |               |
      \  Extract   /              \             /
        \        /                  \         /
          ------                      -------
           ^^^^                        ^^^^^
           Heat                        Heat

       Bruce Hamilton