On Wed, 06 October 1999, George Harris wrote:

> 
> Regarding materials with negative susceptibilities:
> 
> Perhaps I have missed something along the way, but there are a number of
> materials with higher negattive susceptibilities than carbon.  The handbook
> of Chemistry and Physics (59 th edition - 1979) lists the
> following:
> 
> Carbon or diamond   -6
> Bismuth (solid) -280
> Aluminum Sulfate (anhydrous) -93
> Aluminum Sulfate Hydrate (Al2(So4)3.18H2O -323
> Calcium Carbonate  -38
> Ammonium  Nitrate  -34
> Ammonium Sulfate  -67
> 
> The values stated are per gram, so the specific gravities are probably
> important also.   It would seem that the crystal form should be the best if
> available.  Have any of these been tried?
> 
> George Harris
> 

George,

Thanks for the above info.  Without the benefit of
having any such book and reference, its nice to see
such.  As I understand it, alot of the recent
editions lack any such reference.

Part of the mystery with only carbon and bismuth
is that theres no guarantee (especially with carbon)
that there will even be a diamagnetic field, and
indeed it can be paramagnetic (magnetic).  As I
understand it, some carbon can outperform bismuth.

As far as the above reference this immediately 
brings up the question of what was used to derive
thier figures.  I would suggest its only drawn
from afew samples, and the variation of chemical
analysis in their samples probably were only a 
small portion.  I've read where some carbon, has
a value of up to -450...but, part of the same
"rod" can fail far below that, or even be magnetic.

The real mystery is just what it is, that makes
some with a certain value, and another sample so
very different, from the other?  

Your calcium carbonate (chalk)reference was very 
interesting.  The crystalline varietys come in
calcite and aragonite.  The so called "iceland"
spar" variety of calcite, too me, might be a
interesting object to check out in rock shops,
mainly because they would be more likely to 
have a nice flat surface if any is found that is
diamagnetic.  Iceland spar is the stuff that
shows the double refraction...i.e, a printed
page underneath (on better clear specimens), 
will show a doubling of the print or words.
However, being as I've not yet checked it out,
who knows what the results would be.  I'am also
probably concerned that certain specimens may
be better than others...but I'am just speculating.

Thanks for references, time will tell, with
calcite.  Overall, I think the mystery continues...

Thanks, Meredith Lamb

  


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