iandol on thu 12 sep 02
Dear Roger Graham,
I appreciate your explanation.
But the original quotation given by Autumn Downey was <<....Havas give =
the following figures in % Wt. Cubic x 10^-7/oC....>>
I questioned the use of "Wt", interpreting this as being "Weight", in =
connection with "Expansion", then suggested that there might be some =
connection with "Volume" which prompted both hemispheres the use of the =
notion of "Cube Root"=20
Great to have your input.
Best regards,
Ivor.
John Hesselberth on fri 13 sep 02
Ivor,
I think some researchers have calculated their expansion coefficients so
that when they are used in the rule of mixtures, wt% of the various
oxides should be used. Others have calculated them so that mole
percentages are the appropriate way to use them. The Wt% in Autumn's
message (and those given on David Hewett's web site) are only intended
to indicate that--they are not part of the units associated with the
coefficient.
Regards,
John
On Wednesday, September 11, 2002, at 02:28 PM, iandol wrote:
> I questioned the use of "Wt", interpreting this as being "Weight", in
> connection with "Expansion",
Frog Pond Pottery
PO Box 88
Pocopson, PA 19366
Fax or phone: 610-388-1254
iandol on sat 14 sep 02
Dear John Hesselberth,
Thank your for this information. It seems to me that the situation is =
very confused. There should be some consistency otherwise comparison =
become meaningless.
I would still like to know how it is possible to derive values for =
materials which, though present in theory, are never introduced into a =
raw mixture in their molecular state, eg K2O, Na2O.
Best regards,
Ivor
<<so that when they are used in the rule of mixtures, wt% of the various =
oxides should be used. Others have calculated them so that mole =
percentages are the appropriate way to use them. The Wt% in Autumn's =
message (and those given on David Hewett's web site) are only intended =
to indicate that--they are not part of the units associated with the =
coefficient.=20
Regards,
John>>
John Hesselberth on sun 15 sep 02
On Friday, September 13, 2002, at 04:12 PM, iandol wrote:
> Thank your for this information. It seems to me that the situation is=20=
> very confused. There should be some consistency otherwise comparison=20=
> become meaningless.
>
> I would still like to know how it is possible to derive values for=20
> materials which, though present in=A0theory, are never introduced into =
a=20
> raw mixture in their molecular state, eg K2O, Na2O.
>
Hello Ivor,
I suggest you visit David Hewett's web site. He gives a very thorough=20
discussion of all this including original references that you usually=20
seek. This work was done in the late 1800s and early 1900s so I think=20=
expecting it to be done to a consistent standard is unrealistic.
The url of his site is: http://www.dhpot.demon.co.uk
If I were doing it today I know how I would do it. I would make silica=20=
glasses containing known amounts of the materials I was interested in,=20=
measure their expansions in a dilatometer, compare the results to a=20
silica glass of the same composition but without the material of=20
interest, and extract the expansion of the added material by difference.=20=
You'd probably have to do it at 2 or 3 different levels of the material=20=
of interest to check for variability. This is where you need to decide=20=
whether you are working in wt% or mol% and report your results=20
accordingly. Maybe you could get Ron Roy interested in putting his=20
dilatometers to use this way-- it shouldn't take more than a year or two=20=
Ron.
Regards,
John
Frog Pond Pottery
PO Box 88
Pocopson, PA 19366
Fax or phone: 610-388-1254
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