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watson.fawkes
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Quote: Originally posted by Magpie  | | What the vacuum pump does is remove all the air so that the mercury can be poured through that restriction without having to fight air trying to
escape countercurrently. |
You might be able to get it filled in stages. Your pump will evacuate to about 1/15
of atmospheric, which is to stay that it will evacuate 14 parts out of 15 of whatever gas is there. So instead of fighting counterflows, just get most
of the air out and compress the rest with the mercury column. After that, invert the column and the remaining air will bubble up, but this time
through wide tubing in the close end. Now evacuate again and repeat. Two or three rounds of this should get you enough fill. You should be able to get
about 3/4 fill, say, in the first round.
Another idea. I'm not sure you want to try this one. If you seal off the system while evacuated, a heat gun should decrease the viscosity of the
mercury, while not generating significant overpressure to the glass. You'd really have to heat it to get back to 1 atm of internal gas pressure; there
looks to be a gasket that would fail first. Let it cool while sealed in a position so that the bits of condensing mercury vapor coalesce toward the
reservoir.
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Magpie
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| Quote: Originally posted by watson.fawkes |
You might be able to get it filled in stages. Your pump will evacuate to about 1/15 of atmospheric, which is to stay that it will evacuate 14 parts
out of 15 of whatever gas is there. So instead of fighting counterflows, just get most of the air out and compress the rest with the mercury column.
After that, invert the column and the remaining air will bubble up, but this time through wide tubing in the close end. Now evacuate again and repeat.
Two or three rounds of this should get you enough fill. You should be able to get about 3/4 fill, say, in the first round.
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That seems like it should work. If my current efforts to acquire use of a hard vacuum through a friend at a university do not pan out I will try it.
Thanks.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Magpie
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As stated earlier in this thread I acquired a Bennert manometer but it came unfilled with mercury. I had the necessary mercury (~4mL) but also needed
to be able to pull a deep vacuum (<1mmHg) for the filling process.
Earlier I had bought a Harbor Freight 2.5CFM single stage vacuum pump (now <$100) rated at 75 micron (0.075mmHg). The pump worked well for vacuum
distillations but I was skeptical that it would actually pull a deep vacuum.
After numerous attempts to get others to help me (some sincerely tried, others blew me off) I got fed up and bought my own Pirani vacuum gauge capable
of reading down to 1 micron (0.001mmHg).
Today I set up the system I will need to fill my Bennert manometer. I was delighted when the system pulled right down to 121 micron (0.121mmHg). So
it looks like I'm good to go.
Below is a picture of the system at 121 micron absolute pressure. I'm sorry that I didn't use a flash for the close-up of the gauge reading. You'll
have to trust me on that.
Questions and comments are welcomed. But please don't remind me that now that I have the Pirani I don't need the Bennert.
 
[Edited on 22-11-2011 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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starman
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Hey magpie I have the same pilot plus though directly attached to the pump on a tee.Make sure you always release the vacuum gradually,I did the sensor
on mine and fortunately they replaced the unit on warranty.
Chemistry- The journey from the end of physics to the beginning of life.(starman)
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Magpie
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| Quote: Originally posted by starman | | Make sure you always release the vacuum gradually,I did the sensor on mine and fortunately they replaced the unit on warranty. |
Thanks for the warning, starman. I will keep that in mind although a globe (or needle) valve would be better for that than my ball valve.
I installed the ball valve for isolation of the gauge prior to shutting off the pump. Hopefully this will help in keeping the gauge sensor from being
contaminated with pump oil, etc.
The single most important condition for a successful synthesis is good mixing - Nicodem
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jock88
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Can anyone advise me on controlling this pirani gauge.
http://www.ebay.co.uk/itm/3-three-x-Applied-Materials-Capaci...
Is it simply a matter of putting somewhere between 15 and thirty volts on the correct pins and then perhaps reading the output using a multimeter and
converting voltage to pressure (using a chart perhaps)?
Or do I need a precise controller.
Would this elcheepo controler work.
Applied Materials 0190-27313 Capacitance Pirani Gaug
Thanks
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