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Topic: Vacuum Pumps...  (Read 14509 times)

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Offline KYPowerlifter

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Vacuum Pumps...
« on: January 17, 2009, 05:41:01 PM »
Hello:

[I have been a member here in the past but, for some odd reason, had to re-register]


I've decided to purchase a vacuum pump or some reasonable facsimile. After a degree of looking, I have a question or two...

1) Thoughts on this one: http://images.google.com/imgres?imgurl=http://www.labequip.com/stock/pictures/24178.jpg&imgrefurl=http://www.labequip.com/itemcatalog/stkno/24178/Fisher-Scientific-Maxima-D4A/Rotary-type-Vacuum-Pump.html&usg=__Sxfv0SzQGrHeZle_swCa-JEFim8=&h=385&w=640&sz=33&hl=en&start=1&sig2=vwCC304C243QZiF5M6XHzw&um=1&tbnid=QyCZeWhWj_A8_M:&tbnh=82&tbnw=137&ei=xA9ySfmqGZbGtgfy58HmCA&prev=/images%3Fq%3DFisher%2BScientific%2BMaxima%2Bmodel%2BD4A%2BRotary%2BVacuum%2BPump%26um%3D1%26hl%3Den%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-US:official%26sa%3DN

2) There is one other I am curious about:"Surco Vac vacuum pump. Model: 5711 130. 115 volt. Unit pulls down to 25 inHg."

I have come to question just how much vacuum, in terms of " hg, one needs for the vast majority of experiments that the 'citizen chemist' might engage in. I have come at this problem from two angles, to wit: the notion of using a recirculating system, via a jet pump and a glass aspirator, or using one of the above type pumps with a cold trap (likely improvised).

Price, of course, being the prohibiting factor, I have considered it and it seems close between the two.
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Offline ARGOS++

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Re: Vacuum Pumps...
« Reply #1 on: January 17, 2009, 06:39:29 PM »
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Offline KYPowerlifter

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Re: Vacuum Pumps...
« Reply #2 on: January 17, 2009, 07:32:56 PM »
Indeed!

Your post and the link are helpful. I am aware of the pump parameters but not so much the applications. You explanation in the post answers my question.

If I cannot purchase an actual pump of reasonable quality and 'strength', I will rig up a jet pump and employ a glass aspirator (water jet). I have considered a large plastic tote for a vessel and a 'Sears' 3/4 hp shallow well jet pump (pumps 40/60 psi): http://www.sears.com/shc/s/p_10153_12605_08302518000P?vName=Lawn%20&%20Garden&cName=OutdoorDecor&sName=Fountains%20&%20Pumps&psid=FROOGLE01&sid=IDx20070921x00003a along with a glass aspirator:  http://kantu200scientificstore.ecrater.com/product.php?pid=2634947 and give that a go.

Thank you
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But it is the knowledge of necessary and eternal truths which distinguishes us from mere animals, and gives us reason and the sciences, raising us to knowledge of ourselves and God. It is this in us which we call the rational soul or mind. -GWL

Offline ARGOS++

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Re: Vacuum Pumps...
« Reply #3 on: January 17, 2009, 07:40:09 PM »
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Offline KYPowerlifter

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Re: Vacuum Pumps...
« Reply #4 on: January 19, 2009, 09:43:30 PM »
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But it is the knowledge of necessary and eternal truths which distinguishes us from mere animals, and gives us reason and the sciences, raising us to knowledge of ourselves and God. It is this in us which we call the rational soul or mind. -GWL

Offline ARGOS++

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Re: Vacuum Pumps...
« Reply #5 on: January 19, 2009, 09:51:39 PM »

Dear KYPowerlifter;

Congratulation!!  -  Great, take care for it with a cool trap!

Good Luck!
                    ARGOS++

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Offline KYPowerlifter

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Re: Vacuum Pumps...
« Reply #6 on: January 22, 2009, 03:29:46 PM »
Cold Trap:

These seem to be quite expensive but very necessary. Argos has been extremely helpful and has me wondering, is their any way of improvisation here?

Is using an acetone/dry ice combination a reasonable substitute for liquid nitrogen?

Lab Setup:

With a view towards organic chem, could you guys give me some tips on basic lab setup vis-a-vis equipment?
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Offline azmanam

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Re: Vacuum Pumps...
« Reply #7 on: January 22, 2009, 03:31:27 PM »
Honestly, I wouldn't use liquid nitrogen.  While unlikely, you have the potential to condense oxygen in a liquid nitrogen trap.  While unlikely, this liquid oxygen has the potential to rapidly expand (i.e. explode).

I'd stick with dry ice/acetone.
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Offline enahs

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Re: Vacuum Pumps...
« Reply #8 on: January 22, 2009, 09:52:50 PM »
Dry Ice and Acetone, or Dry Ice and isopropyl alcohol is usually cheaper than liquid nitrogen, and works pretty damn well. If you are that worried about getting something in your pump, then go through a couple of traps connected in series.

It is true with liquid nitrogen you can at times make liquid oxygen, which is dangerous. But if you pull a vacuum before you put the trap in the liquid nitrogen you will be fine.

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Offline nj_bartel

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Re: Vacuum Pumps...
« Reply #9 on: January 22, 2009, 10:31:53 PM »
wouldn't that defeat the purpose of the trap?
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Offline ARGOS++

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Re: Vacuum Pumps...
« Reply #10 on: January 23, 2009, 12:18:40 PM »
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Offline KYPowerlifter

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Re: Vacuum Pumps...
« Reply #11 on: January 23, 2009, 03:58:20 PM »
Whew... it looks like liq N could end up being a large investment. Perhaps I am misunderstanding things but it appears that it is much like welding gases, it's the vessel that costs you... I also assume I'll have to find it 'locally', living in Western Kentucky this could prove difficult.

I could be wrong, but "Argos++" is 58 years old, according to his profile, and likely works as a chemist. So I suppose I'll have to trust him.
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But it is the knowledge of necessary and eternal truths which distinguishes us from mere animals, and gives us reason and the sciences, raising us to knowledge of ourselves and God. It is this in us which we call the rational soul or mind. -GWL

Offline KYPowerlifter

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Re: Vacuum Pumps...
« Reply #12 on: January 23, 2009, 04:02:29 PM »
Tried to edit my other post and add this addendum but must have hit "quote"...

Is my second question impossibly vague, re: lab setup?
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Offline ARGOS++

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Re: Vacuum Pumps...
« Reply #13 on: January 23, 2009, 05:03:54 PM »
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Offline enahs

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Re: Vacuum Pumps...
« Reply #14 on: January 23, 2009, 07:25:46 PM »
Quote from: nj_bartel on January 22, 2009, 10:31:53 PM
wouldn't that defeat the purpose of the trap?

No.
You set up what you are going to pull a vacuum on with a valve. Close the valve and turn on the vacuum. This will be a closed system and remove all the oxygen from the trap. Then you put the trap in the liquid nitrogen, and then you open the valve to your container and pull the vacuum on your chemistry!
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