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Re: Problem with a Barometer



Roger: Perhaps your meter stick is corrected to sea-level? ; )

Actually, I'm wondering if the barometer has been stored near volatile
hydrocarbons. (The chemist in me is talking again.) I've done a lab
where students measure the vapor pressure of hexane (one notch lighter
than gasoline, and pure) and one time some of the hexane distilled into
the mercury. This reduces the density of the mercury, with the effects
you observe. It was surprising to see a U-tube manometer open to air on
both sides, with one side (the one that had been hooked up to the
hexane) higher than the other. Careful heating under vacuum solved my
problem: not an option for a barometer. (I doubt I distilled any mercury
out, since the hexane boiled as low as 50 C.) Carefully replacing the
mercury will do the job. Replacing it with an anaeroid manometer would
be my first choice, for the health reasons mentioned.
David

--
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Dr. David W. Steyert steyert_dw@mercer.edu
Department of Chemistry (912)-752-4173
Mercer University
Macon, GA 31207
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