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Re: Fortin Barometer Repair



The need for a clean tube and clean mercury has been stressed. A good
way for filling the tube has also been described. Cleaning the tube
with nitric acid has been mentioned. These are all good pieces of
advice. So far no one has mentioned how to clean the mercury.

Mercury can be cleaned quite well with a very simple procedure. The
types of impurities that cause problems in a barometer are the
impurities that form a "slag" on the surface of the mercury. These are
removed by running the mercury through filter paper with a small hole
in it.

Get some filter paper and a glass funnel from the chemistry folks.
Fold the filter paper into quarters like you would usually do for
placement in a glass funnel. Poke a hole right in the point of the
paper. A pinhole is probably a bit too small unless you wiggle the
needle to make it a tad bigger. An unfolded small paper clip might be
about the right size for poking the hole. Anyway, after you have the
paper folded, hole poked, paper in the glass funnel, clean beaker in
place to catch the mercury... slowly pour the mercury through the
paper. The slag sticks to the paper and the clean mercury runs
through. It's quite amazing how well this works.

Some people think they have to distill mercury. This is hazardous
because of the mercury vapor and I do not recommend it. It is totally
unnecessary for the type of cleaning needed for a barometer.

Some advocate getting rid of mercury in labs. I do not see this as a
necessity if you take precautions to keep it contained. As much as
possible, manipulate the mercury over a plastic wash tub/tray. Any
spills can be tipped into a corner of the tub and reclaimed.


Michael D. Edmiston, Ph.D. Phone/voice-mail: 419-358-3270
Professor of Chemistry & Physics FAX: 419-358-3323
Chairman, Science Department E-Mail edmiston@bluffton.edu
Bluffton College
280 West College Avenue
Bluffton, OH 45817