[wxqc] Mercury Barometer

Mark Wyman mark at markwyman.com
Wed Dec 17 12:12:59 CST 2008


Somewhere there is a telescope that uses Mercury as a mirror since spinning
it makes a parabolic shape, and thus a nice mirror for imaging.

 

http://en.wikipedia.org/wiki/Mercury_mirror

http://www.newscientist.com/article/dn14030-liquidmirror-telescopes-are-a-re
ality-at-last.html

 

 

And no, I am not suggesting being unsafe about hazardous substances. Like
anything else it requires common sense. But to outlaw them completely for
industrial use is absurd since many industries rely on these substances to
get high quality product. Yes, there are alternatives, in most cases, not
necessarily as good.

 

Mercury for a barometer is nice in the sense you don't have to go through a
complex calibration and temperature compensation scheme with a lot of
expensive equipment to give accurate output. The mercury barometer will also
continue to work 50 or more years from now just as well as today. The
electrical/silicon equivalent will fail over that time as gasses will slowly
migrate through the thin layer of silicon over the vacuum chamber, and
eventually your reading will not be in reference to 0, and there is nothing
you can do to correct it apart from tossing out the sensor and getting a new
one.

 

And try to read an electrical version without power?

 

However nothing works as good as lead/tin solder for long-term reliable
circuit board construction, yet you cannot use it due to RoHS for commercial
applications. It is a good thing there are exceptions to this in avionics
and space, otherwise over a period of high shock and vibe,
plane/satellite/military circuitry would just fall apart. 

 

Silver solder stratifies over time with heat changes and shock/vibe, and
it's crystals align oddly, sometimes resulting in extremely weak joints that
just fall apart. Also the tin in the silver solder will form tin whiskers
through electro-migration without the presence of lead or encapsulation and
simply short out circuitry over time. However we are saving future
generations by not putting lead back in the ground where we got it from.
Don't let your kids play outside, there are tons of hazardous substance in
the dirt, not including parasites.

 

-Mark

 

From: wxqc-bounces at lists.gladstonefamily.net
[mailto:wxqc-bounces at lists.gladstonefamily.net] On Behalf Of Victor Engel
Sent: Wednesday, December 17, 2008 12:50 PM
To: Discussion of weather data quality issues
Subject: Re: [wxqc] Mercury Barometer

 

I recall a photograph in Natural Geographic of a man sitting on a vat of
mercury. I just googled and found this:

http://www.theodoregray.com/PeriodicTable/Images/MercuryMiner.JPG

Not sure if it's the same picture.

Mercury used to be used in gold mining because gold dissolves in mercury. I
think the process was to boil off the mercury leaving gold behind. That,
obviously, would be extremely dangerous, releasing vast quantities of
mercury vapor into the air.

Victor

On Wed, Dec 17, 2008 at 10:40 AM, Jim Crumly <jimwc at frontiernet.net> wrote:

Victor

I believe the tube we used was about 36" long.  The process gave us the
process of heating the glass tube to seal it as well as how a barometer is
made and yes we did measure the pressure every day.

I don't remember how accurate it was but it was a learning experience and
may have sparked an interest in weather observation.   I was the one doing
the dunking of the tub in the bowl and I remember watching the level of the
mercury in the bowl coming up to just below the rim of the bowel and
wondering if it would overflow it didn't but was close.   I believe I have
more problems from "Agent Orange" than the mercury. I think we are showing
off our age here.

Jim

CW4367 

 

From: wxqc-bounces at lists.gladstonefamily.net
[mailto:wxqc-bounces at lists.gladstonefamily.net] On Behalf Of Victor Engel
Sent: Wednesday, December 17, 2008 9:05 AM


To: Discussion of weather data quality issues
Subject: Re: [wxqc] Mercury Barometer

 

We used the same method in grade school. The difference was that the tube we
used was list a test tube, only longer, so already sealed.

That barometer stayed as a permanent fixture in the science room.

Victor

On Wed, Dec 17, 2008 at 10:00 AM, Jim Crumly <jimwc at frontiernet.net> wrote:

Victor & A.J.

I remember making a barometer in science class ether Jr. high or freshman
High School. (early 60's anyway) we used a long glass tube filled with
mercury  a small bowl  of mercury and a ruler.

The process was to seal one end of the glass tube then fill it with mercury
then fill the bowl about half full then (oh my god) place your finger over
the open end of the tube and immerse it in the bowl and release it letting
the mercury seek the correct level for the pressure. And yes it did measure
the barometric pressure with a ruler set beside the tube. 

 

Jim

CW4367

 

From: wxqc-bounces at lists.gladstonefamily.net
[mailto:wxqc-bounces at lists.gladstonefamily.net] On Behalf Of Victor Engel
Sent: Wednesday, December 17, 2008 7:57 AM


To: Discussion of weather data quality issues
Subject: Re: [wxqc] Mercury Barometer

 

I just got an email from Jim Mulhern at Medford Clock and Barometer, who
says he still makes Princo barometers.

Victor

On 12/15/08, Victor Engel <brillig at gmail.com> wrote:

Have you tried Medford Clock and Barometer? Maybe you can get an antique one
there:

http://www.medfordclock.com/barometer/antique.htm

On Sun, Dec 14, 2008 at 12:15 PM, A.J deLange <ajdel at cox.net> wrote:

You can forget my suggestion about buying a mercury barometer. Apparently
you can't because the only manufacturer (of which I am aware i.e. Princo)
stopped making them over a year ago citing  increasing regulations
concerning mercury. The lawyers, politicians and tree huggers have done us
in, folks. The cancer is metastatic. But we let it happen.

Does anyone know of another source for these dangerous instruments (which
used to hang in the chemistry lab in every high school in this once sensible
country)?

A.J.
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