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Is there anyway to get a hard vacuum using chemicals?

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LAN_403

Wastrel

Wed Nov 09 2011, 06:21PM

Registered Member #4095 Joined: Thu Sept 15 2011, 03:19PM
Location: England.
Posts: 122

Ocean Waves wrote ...

good luck, and I recommend mercury its far safer than gallium IMO, though more expensive

I think you have this backwards...

I've been trying to find a way to make one of these without mercury but indium, gallium and their alloys stick to glass. Pthallates used for diffusion pumps dissolve oxygen. I've read a number of reports of using low melting alloys, woods metal etc, and the gist is that when they cool the freezing alloy expands and destroys the pump.

Take ultimate pressure readings of the Sprengel pump with a pinch of salt if they are below the vapour pressure of mercury. Mercury vapour is a condensing gas in a McLeod gauge.

klugesmith

Thu Nov 10 2011, 12:43AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Ocean Waves wrote ...

damit, no sooner did i say i havent seen one did google turn one up, so here is my foot in my mouth lol, notice this little blurb at teh top says 1/100 of an atmosphere thats about 10 microns.........

You should be more careful when uncritically repeating numbers found online, or presenting your own calculations unreviewed.
1/100 of an atmosphere is about 7600 microns.

Your page 57 reference gives a pretty spectacular claim of 1/90,000,000 atmosphere.
That's about 0.8E-5 torr, or 0.008 microns, far below the vapor pressure of Hg at ordinary temperatures. I wonder how Professor Rood measured his vacua?

Ocean Waves

Thu Nov 10 2011, 06:57PM

Registered Member #4181 Joined: Thu Nov 03 2011, 02:39PM
Location:
Posts: 42

IMHO don't really have it backward on gallium, having worked with and refined large quantities of mercury I find the prospect of working with gallium to be more of a hazard, as it sticks to everything but teflon in very thin layers, and as such has a greater chance to be absorbed into your body in greater quantities where it can react and form toxic compounds in greater quantity that are cumulative, where mercury is considered toxic it has a lower chance of absorption, as well our bodies have efficient mechanisms in place to remove safely up-to 500 mcg per day, which is a dosage you are not likely to get unless you inhale the vapors in a closed space for an extended period of time or ingest it. You have to understand mercury was considered non-toxic until some contaminated fish in japan killed 50 people at a restaurant. Because when it was discovered that 1 fish can absorb enough mercury and store it as a toxic organometallic fatty acid in quantity to kill 50 people, a very large movement to label mercury as toxic and remove it from use came into to play, before this mercury was everywhere including schools as large pools in classroom barometers where students would steal it and allow it to get loose all over the grounds. Ingested Liquid mercury was even widely used as a treatment for heart burn and stomach ulcers. Until just recently mercuric nitrate was still used to treat â€œQ-Tipsâ€ for sterile purposes...................wounder when gallium will have its day?

My over all opinion is that the danger of elemental mercury to the individual is exaggerated, However the overall danger to the environment in general where it can be changed into highly toxic methylated organometallic compounds by fish and plants cannot be any closer to the truth or underestimated.
While there is a level of environmental precaution needed when handling a spangel pump with mercury, it could be completely mitigated by designing the pump so that the mercury can be lifted without exposure to the user, requiring no safety equipment while using, and venting the output of the pump outside away from the user What is of a greater concern than the user, Is that to the environment the use of a containment should the pump completely shatter to prevent the mercury escaping is really the most important aspect of consideration in operating such a device in my opinion..................... nothing special need be used, just anything that is water tight would also be mercury tight.......preferably with a sloped drain to a collection flask

Truth is I believe that mercury can be handled safely as another element that has a tendency to form toxic salts. If you haven't noticed yet I'm not big on preaching safety lectures, I find such practice to lay strife and deterrence to practical endeavors, instead I advocated the heavy use of common sense and informed research.

That Said my procedures for working with large quantities of mercury daily are simple, don't ingest it, don't allow per-longed skin contact if it can be avoided, do not wear gloves as they can cause absorption in practical use, don't breath in the dust from top layer of the metal, the latter being more troublesome keeping a slight detergent or alkaline sol in distilled water on top of the mercury will prevent the formation and mobility of such dust and will also keep volatile oils from having contact. Finally do not touch mouth, face or membranes. Wash hands and face with soap and water prior to eating drinking or smoking, shower and change clothing at the end of working working day. So as not to take any obnoxious ions home with you. Yes we still use batch amalgamation to collect precious metals here in the US.

If you disagree with me thats fine everyone is entitled to there own informed opinions, and to take whatever calculated risks they choose.

If you are still afraid of mercury there is nothing that states that you have to use glass for a pump. Metals will work just as well, just select one that is not easily alloyed mercury or gallium, also if you have to use gallium it doesn't matter that it sticks in thin coatings, just drain most of it from the device before it freezes, besides how hard is it to keep gallium at 29 C thats less than body temperature? Alcohol burner? Fireplace? Use your imagination.
there is nothing that states that you have to use a glass for a pump, other metals will work just as well, just select one that is not easly alloyied

Hon1nbo

Mon Nov 14 2011, 08:19PM

Registered Member #902 Joined: Sun Jul 15 2007, 08:17PM
Location: Pacific Northwest USA
Posts: 1042

I saw a Scientific American Amateur Scientist article that used a certain chemical to rapidly absorb the air around it. I don't recall it requiring liquid nitrogen, I think it may have used dry ice (though that could be my memory failing me)
I'll try to dig up the article if I have time (I have the CD with all of them).

-Jimmy

Conundrum

Wed Nov 16 2011, 07:32AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

Gallium metal is a pain, it DOES stick to everything however this can be avoided with a simple coating of tin oxide on the glass.
I don't think its particularly toxic however I would be careful as it can rapidly corrode some metals including aluminium which could be a fire hazard in the presence of flammables such as wood.

In-Ga-Sn alloy is liquid at room temperature however.

-A

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