High vacuum CHEAP and dirty!

wow!

what about some antimatter?
it will annihilate the norml matter so leaving you with PERFECT vacuum, of course some virtual particles could be formed from the energy that is around, but if you are smart and do this at 0°K it won't be an issue.

BIG SIGH!!!

You guys know what a diffusion pump is!!!

From Wikipedia, the free encyclopedia.


Diffusion pumps use a high speed jet of fluid to direct residual gas molecules in the pump throat down into the bottom of the pump and out the exhaust. The high speed jet is generated by boiling the fluid (typically silicone oil) and directing the vapor through a multistage jet assembly. Often several jets are used in series to enhance the pumping action.

Unlike mechanical pumps, diffusion pumps have no moving parts and as a result are quite durable and reliable. They can function over pressures ranging from about 10-10 torr to about 10-2 torr. Diffusion pumps cannot discharge directly into the atmosphere, so a mechanical forepump is typically used to maintain an outlet pressure around 0.1 torr.

One major disadvantage of diffusion pumps is the tendency to backstream oil into the vacuum chamber. This oil can contaminate surfaces inside the chamber or upon contact with hot filaments or electrical discharges may result in carbonaceous or siliceous deposits. Due to backstreaming, diffusion pumps are not suitable for use with highly sensitive analytical equipment or other applications which require an extremely clean vacuum environment. Often cold traps and baffles are used to minimize backstreaming, although this results in some loss of pumping ability.
--------

also note that sophisticated multistage diffusion pumps with atomic scavengers have been able to pull repeatable vacuums in the range of 10 to the neg 21 torr

and some labs have claimed 10 to the neg 23 torr, although those results have been hotly contested (thats like one atom per meter cubed, or something equally ridiculous!)

anyway the point is that you would be able to have a strong vacuum on tap which might be good for ambient temp fractional distilliation/sublimation of some of these energetic compounds you guys keep talking about/

and perhaps you could use the "unused" vacuum to regenerate your drierite?

whatcha think?.... McGyver's and McGyvette's!

[Edited on 29-11-2003 by Hermes_Trismegistus]

Jesus!

diffusion pumps

YUP! actually it would be strong enough to evacuate your whole damn fume hood out of your window via tubing, but it's not really for such an application, you may simply want to use a squirrel cage blower for something so easy.

the purpose I think such a pump would be good for would be to lower pressure quite a bit more substantially than that afforded by a duo-seal mechanical pump.

like say you wanted to distill high boiling fractions in AMBIENT temperatures, with a diffusion....I am sure you could boil water with the heat of your hand and such.

Lets say you wanted to distill a temp sensitive product (like nitroglycerin) it would be nice to do so without adding heat wouldn't it?

I am not an explosives guy, but I am certain high vacuums could provide HOURS of fun for many the amateur scientist (if not always practical)


Its just that I see them up for auction frequently on labx and they look soooo tempting and pretty

sooo PRECIOUSSsss, my preaashezzzzz!!

Sci. Am. ran a few columns on vacum techniques just before the amatuer science column went under . Molecular sieves are recommended instead of activated charcoal unless you're trying to form an explosive.
BTW, I like the rotary vain pump. From the "Journal of Unpublished Chemistry":

Your logic is impeccable, Unionised. I think there I may be overpaying for my university education. , and Soooo... by running a medium with a much higher vapor pressure than water through the aspirator...like a heavy oil...sigh!

also, I have been meaning to ask you...Is your name related to a quip in an article Isaac Asimov wrote in the March 1963 issue of the Magazine of Fantasy and Science Fiction, "You Too Can Speak Gaelic"?

Vacuum on the Cheap: the Refrigerator Compressor?

sarcosuchus

Mendeleev; re-Diffusion Pump, I have done a little research on this, but no more than perhaps three hours total.

From what I understand of the diffusion pump, the answer is about capacity is both yes and no.

Yes it does "exhaust" an amazingly large "volume", but since most only seem to be designed to begin work at pressures less than 1mmHg, (they require a mechanical forepump), it might not really add up to that much in the total mass of air moved. (moving hundreds of litres of almost total vacuum per minute is almost a peculiar concept to grasp intuitively)

and yes, bigger pump, bigger volume.

P.S. I have since found out that most common metals are pretty much totally unsuitable for making serious diffusion pumps, not only do they carry one helluva load of absorbed....?.adsorbed....?, aw fuckit....I can't remember...

Anyway, the gasses come out slowly out of the metal when you pull a high vacuum and kill your vaccuum. Metals can also be somewhat permeable to some enviornmental gases, most notably, stray helium atoms.

However, glass can be fairly easily "de-gassed". By strong heating and other means.

depends how high a vacuum and what sphere of science.

Pro Chemical labs seem to use almost everything water aspirators, piston pumps, diaphram pumps, and rotary vanes. (application dependant)

Serious physics labs tend to go directly to multiple rotary vane pumps hooked in series with multiple stage diffusion pumps.

Those physics boys certainly do like to be vacuous.

Yeah, them physics people love absolute vacuum, fictionless sufaces, and massless ropes and pulleys, etc . The job of applying it to real world is up to the engineers. Also while looking wikipedia at that vacuum pump article you mentioned Hermes, I also found this:



Ion pump
From Wikipedia, the free encyclopedia.
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Sputter ion pumps are a class of vacuum pump designed to operate in very low pressure (i.e. very high vacuum) conditions. They operate by ionizing a gas within a magnetically confined cold cathode discharge. The events that combine to enable pumping of gases under vacuum are:

Entrapment of electrons in orbit by a magnetic field.
Ionization of gas by collision with electrons.
Sputtering of titanium by ion bombardment.
Titanium gettering of active gases.
Pumping of heavy noble gases by ion burial.
Diffusion of hydrogen and helium into titanium.
Dissociation of complex molecules into simple ones for pumping ease, e.g., CH4 breaks down into C and 2H2. Hydrogen is pumped separately. Carbon is no longer part of the residual gas and resides in solid form.
Burial is the basic means of pumping heavy noble gases. Argon ions neutralized via glancing collisions with a sputter cathode impact the pump wall and are coated with sputtered titanium. Triode pumps are specially designed to maximize the kind of collisions that produce energetic neutrals.

Argon is permanently pumped on the wall behind the cathode in these pumps. The wall area receives titanium for inert gas burial but, because of a retarding electric field between the cathode and the wall, it is not subjected to ion bombardment and thus gases are not resputtered.



Not too shabby eh?

Thank you Mendeleev. I have seen the Welch belt driven single stage pumps advertised. Apparently the belt drive provides low pump speed. This in turn allows reaching a 1 mmHg vacuum with only 1 stage. It also decreases pump wear.

It looks like selecting a lab vacuum pump is about as confusing as trying to decide what type of boat to buy. They all have their pros and cons. I think it signigicant, however, that the mother of all lab supply houses only offers a 2-stage, oil-filled, direct drive pump (rotary vane I presume) for their "high" vacuum.

[Edited on 14-12-2004 by Magpie]

Aspirator

Yes. That does look like a good vacuum, but I doubt you could quickly evacuate something with 15cc strokes. Also remember the ridiculous price tag... I've seem better aspirators on ebay for <$2.

Vacuum

Air compressor into vacuum pump