>No, in my opinion, the Micronizer is the best method for grinding
>most kinds of materials for XRD. A few years ago I did a fairly
>extensive comparison of grinding methods using a laser diffraction
>particle size analyzer to measure the size distribution produced
>by various grinders. The McCrone unit reduced quartz (sand) to
>< 2-3 microns in 15 minutes -- nearly perfect for XRD quantitative
>analysis.
>
>The unit has other advantages: Since the unit uses wet grinding,
>there is minimal change in crystallinity of the sample. Also,
>since all is done wet, between sample cleaning is easy, and there
>is no cross sample contamination.
>
>The cost is a disincentive to some, but if you're grinding lots
>of samples, I find it hard to imagine anything better. They're
>pretty sturdy, since we've used some units for > 15 years. It
>does take some tweaking to find the optimum operating conditions.
>
>Tom Edwards
>Mobil R&D
>
>
Just a query about the use of lazer (and other?) particle sizers
and their accuracy?
When McCrone micronising sulphide ore samples (10 minutes per gram
in ethanol), laser particle sizing gave an average particle size of
5.9micron. However, after giving the identical samples to the site
petrologist/mineralogist to estimate particle size from SEM, he gave
an average based on visual observation of 2 to 3 micron
(there was the occassional 5 micron particle). This means a big difference
in using a microabsorption "fudge factor" on the 13 ID'd phases in
the sample.
Has anyone had similar experiences with laser particle sizers vs visual
estimation?
--------------
On a similar vein, has any one had much fun and feel confident using
microabsorption corrections for quantitative analysis - without knowing
the supposed "real" answer in advance. Or is there the impression they
are presently very much a fudge factor to help get the "right" answer?
Thanks in advance,
Lachlan.
Lachlan Cranswick _--_|\
Melbourne PC User Group, Australia / \
E-mail : lachlan@melbpc.org.au \_.--._/
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