David,

We sometimes use LN2 also with occasional ceramic-mortar failure.  This is
normally for fish (oily) or other samples that won't work well in our ball
mill and must be done individually.

For dried plant material, relatively large, coarse pieces are first
pre-ground in a Wiley Milld to about 20 mesh.  A small handheld coffee
grinder substitutes for the Wiley Mill with less sample loss. The ground
material is then transferred into jars with 2 steel balls of slightly
different size for a night on the ball mill.  The ball mill essentially is
just a belt driven orbital shaker with a custom box on top that contains a
closed cell foam block drilled to accept about 45 small Gerber baby-food
jars.  Baby food jars have a large opening, are shallow, and have a nice
round inner bottom edge for the balls to ride in.  Needles grind up without
any pre-grinding in a day.  Results are best with only jars only 1/8-1/4
full or so.  Occasionally the jars break so we just slip them into sandwich
baggies so that we can recover the material.  The jars are cheap, expendable
and obtained in ready supply from our friends at our local child-care
center.

RS

>From: David Wheeler <[log in to unmask]>
>Reply-To: Stable Isotope Geochemistry <[log in to unmask]>
>To: [log in to unmask]
>Subject: Re: Grinding plant material
>Date: Tue, 13 Mar 2001 11:24:34 +1000
>
>I have another example of LN2 cracking an agate mortar and pestle.  The
>first few 10s of samples went OK then perhaps I got a bit heavy handed
>with the LN2 and/or the stress got too much.  The agate didn't break but
>there was a LOUD 'bang' and a crack appeared.  12 months later it is
>still in one piece but I won't go near it with LN2 again.
>
>Another student discovered that the cheap ceramic mortar and pestle go
>very brittle.  None broke while in use but afterwards they broke into
>many pieces as soon as he touched them.
>
>I'd be very interested to know if the Al oxide works OK.  I now have to
>use a Tama rock grinding mill which is a bit like using a sledge hammer
>to crack a peanut.  I would like to find a viable (i.e. effective and
>affordable) alternative.
>
>cheers,
>David
>
>"Patrick D. Anderson" wrote:
> >
> > I have some plant material that I am having trouble grinding. I thought
> > of using liquid N2 to freeze it the grind in mortar. I have an agate
> > mortar and am wondering if it can survive holding liquid N2? I would put
> > plant material and a small amount of liquid N2 in the mortar and then
> > grind as the N2 evaporates.
> >
> > Thanks
> > Pat
> > --
> >
> > Patrick D. Anderson
> > Researcher
> > Great Lakes WATER Institute
> > Univ. of Wisconsin-Milwaukee
> > 600 E. Greenfield Ave.
> > Milwaukee, WI 53204
> > Phone: 414-382-1731
>
>--
>_______________________________________________________________________
>David Wheeler                 E-mail    [log in to unmask]
>School of Geosciences         Phone     02 4221 3426 (w)
>University of Wollongong,               02 4226 3584 (h)
>Northfields Avenue,           Fax       02 4221 4250
>Wollongong, 2522,
>NSW
>Australia
>
>'stand on hills of long forgotten yesterdays'
>_______________________________________________________________________


-------------------------------------------------
Robert D. Stickrod II, Lab Manager
Idaho Stable Isotopes Laboratory
  www.its.uidaho.edu/isil
Department of Forest Resources
College of Natural Resources, 214
P.O. Box 441133, University of Idaho
Moscow, ID 83844-1133, U.S.A.
[log in to unmask]
lab: (208) 885-6512
fax: (208) 885-6226
-------------------------------------------------

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