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Regolith
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Posts: 73
Registered: 4-2-2011
Location: Mining the moon.
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Mood: Glacial
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Oh it's not for me  , I agree. You also missed the freaky dangerous voltages
required on said monster tubes. I didn't choose the tubes I just build what the customer wants. In this case it's not going to run as a pentode,
single ended triode instead.
I add though that compared to transistor sound... I'll take tubes from a crashed aircrafts avionics 
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IrC
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Actually I did not miss them they missed me. On purpose of course I am always very careful when working with instant death. Been doing it for 50
years. I used a plate transformer from a WWII 10 KW HF power amp to run the tubes when I built that coil. Usually I seldom play with tube types.
Nothing beats a 14.4 KV 15 KVA pole pig for TC building. I still have 3 of these pole pigs left but have not lived anywhere to play with my monster
coils in over 10 years. So I guess your right I do 'missed' the fun of it.
"Science is the belief in the ignorance of the experts" Richard Feynman
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Regolith
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Oh god, pole pigs. Never screwed around with one of them, yet. The large ground transformers from say a school, yes. But not neighbourhood powering
monsters. Tesla coil guys are in that category of people I respect even if I have more knowledge in general (not you, I have friends that are like my
life, insane). It's like working with venomous snakes. Your still alive when you really shouldn't be, kudos
Hey, your into tesla coils. What is the attraction? I mean super insane high voltages(duh), but is there a quest for science behind it ? Have we not
yet achieved some kind of dimension warping energies that are being sought ? Or is it just 12 foot arcs for the fun of it ?
The Sandia Z machine not withstanding, which may actually be tapping some as yet unknown energies.
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IrC
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A - dimension warping energies that are being sought
B - super insane high voltages
C - just 12 foot arcs for the fun of it
A - What I tell people
B, C - the secret truth
However it may be I just like toys.
 
[Edited on 2-25-2011 by IrC]
"Science is the belief in the ignorance of the experts" Richard Feynman
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starman
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Hi IrC,this ebay shop has a number of gauges available.Do you think its worth the money for the one with the pirani sensor(inficon about $190)?
I recently purchased the small rotary vane you mentioned in another thread and am looking at setting it up.
My main initial use is for distillation of organically derived high boilers (long chain alkylphenols over 400c @ atm).
Im looking for a bit of advice as to setting up the manifold and trap within the bounds of economy.
Should I be looking at refrigeration specialist fittings for elbows and Ts etc or are standard brass fittings adequate.
Also,given the nature of the substances I am distilling,to what extent is it necessary to cool the trap.
Any futher advice and tips from you or other members most welcome.
Chemistry- The journey from the end of physics to the beginning of life.(starman)
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Lord Emrone
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I regularly dry ammonium nitrate (completely dissolved in water) on my stove, but it's inside and produces a lot of moisture in my house ...
Maybe I should drive the water out with vacuum drying (outside), but I'm not really into chemistry ... Is there a relatively cheap and easy way to
vacuum dry or does it require a lot of studying ?
Is this pump appropriate for my purposes ?
http://www.aircoshop.nl/accessoires/vacuumpomp
this with a spherical-shaped flask and tube is all I need then ?
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watson.fawkes
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If you're trying to
control distillations, a Pirani gauge isn't just expensive, it won't work over the range of regulation you're looking for. They don't start working
until you're down about about 1 mmHg, and that's too low to be useful if you're trying to manipulate boiling points.
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peach
Bon Vivant
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Starman,
You will likely find most of your high boiling points drop to around 100, depending on the pump, the oil, your condenser and how well sealed up it all
is. You can afford to go down to around 30C before a tap water condenser will start entirely loosing the distillate. It is better to be a few tens of
degrees higher to be sure, particularly if you live somewhere hot, where the distillate flask could warm up to 30C. A pump with a ballast on it is
handy for avoiding that, so you can raise the pressure a little if the thing isn't condensing properly. If it doesn't have one, you can always add it.
The problem with rotaries is volatile solvent. E.g. removing it all post reaction you'd need a dry ice / LN2 trap or it'll go straight through the
condenser and on to the pump if it's not been ballasted up a significantly higher pressure.
I've listed the rough minimum pressures you can use with a tap water cooled condenser for a few different volatile solvents here, if you'd like to
have a peruse to get an idea.
Brass should be fine, but I'd tape up the threads since it costs tens of pence for a roll and will only help with blocking any remaining gaps in the
threads.
[Edit]Watson is correct that Pirani's go wonky as the pressure goes up. For air and nitrogen, they start doing it around 100mBar, but are still
somewhere near linear up to 1 atm. Above 1mBar, they're scrambled if the gas is significantly different to air or nitrogen; e.g. argon, or whatever
you're distilling.
Those HVAC gauges, I've taken one apart and they do use a hot element. The one in mine also had a little thermistor of some description poking into
the side of the tube the element was in. So I would assume they are single wire Pirani's, which behave in a similar way.
It depends a lot on what you're distilling, what information you need to know from the distillation and what else is in there. If you're just trying
to clean up something where you know the majority of it is your material of interest, you don't necessarily need a gauge to begin with, just a stable
temperature on the thermometer. If you're trying to split close boiling points of not well known mixtures, and use the temperature as evidence, you do
need a gauge. It also needs to be one that displays an actual number, not a region of pressure. You can check rough purities, for example, without a
gauge, based on whether or not the temperature sits still in the first place and if so, how long it does it for compared to the rest of the
distillation. You can also add ballast to raise the BP so it'll condense better without a gauge, but again, you can't then work out what is coming
through without knowing the pressure, so you'd have to know before hand or split samples and test it afterwards by some other means.
If you're distilling something that boils at 400C at 1atm, you can manipulate the temperature by around 20-30C whilst staying in the linear region of
a hot gauge. But for wider variations, it's unlikely to be happy.
Unfortunately, the range from distilling volatile solvents to high boilers is within the range where you could really do with more than one gauge. So,
unless you need to know the temperature and pressure simultaneously, you may be better thinking around it by other means. Quite a few
things can be overcome by ideas like contras below. Set the temperature you want to work at, drop the pressure until it appears. Or, if you're
splitting something and know the substrate boils cooler than the product, discount the first fraction through.
Here's an example of a Pirani going off the rails.
[Edited on 6-3-2011 by peach]
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Contrabasso
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Think of getting the boiling flask up to about 50 or 60C then building up the vacuum til the condensate forms in the middle of the condenser.
If you distil at much lower temperatures then you risk losing distillate into the pump and killing the pump.
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Lord Emrone
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Quote: Originally posted by Lord Emrone  | I regularly dry ammonium nitrate (completely dissolved in water) on my stove, but it's inside and produces a lot of moisture in my house ...
Maybe I should drive the water out with vacuum drying (outside), but I'm not really into chemistry ... Is there a relatively cheap and easy way to
vacuum dry or does it require a lot of studying ?
Is this pump appropriate for my purposes ?
http://www.aircoshop.nl/accessoires/vacuumpomp
this with a spherical-shaped flask and tube is all I need then ? |
can someone please answer my questions ? ;-)
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Picric-A
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If your not really into chemistry what are you using the Ammonium Nitrate for?
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starman
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Watson,Peach and Contrabasso thanks for the replies.Inficon claims the following performance data
Base unit includes 9V battery, filters, storage case
Battery life 45 hours
Power source 9V alkaline battery (included)
Refrigeration fitting 1⁄4" male flare
Controls On/off, unit selection, quick calibration
Display units microns, Pascal, millibars, Torr
Display range atm (760,000 microns) to 1 micron
Auto shut-off After 60 min; last reading displayed
when restarted
Accuracy >200-<150,000 microns: 5% of reading,
<200 or >150,000 microns >5% of reading
Resolution (increments) microns: down to 1-micron
Pascal: down to 1-Pa
mbar: down to 0.01-mbar
Torr: down to 0.001
Maximum overpressure 150 psi (7.76 x 106 microns)
Warranty 1-year replacement
It didnt occur to me to that the performance might be affected with different gases ,vapours etc.
Impulsive me ,I've already bought it.So I'll chime back later after I have a chance to check it out.
Regarding my vacuum trap question (which I didn't phrase well) basically I'm assuming the vapour pressure of the condensate of these high boilers is
low enough to avoid using a trap at all.
I'm looking at a bulb to bulb distillation of a substance that the literature has distilling at 151C @ 0.05mm Hg (torr)
[Edited on 11-3-2011 by starman]
Chemistry- The journey from the end of physics to the beginning of life.(starman)
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Lord Emrone
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Energetic Materials.
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Arthur Dent
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Last week I was at my favorite surplus lab equipment store and I picked-up a brand new vial of Beckmans vacuum grease. it's listed in every lab supply
catalog at around $50 and up. Only paid five bucks for it! God I love that place!
Anyway my point is this... for a while, I have been using for my ground glass joints some "silicone dielectric compound" from Canadian tire at $7 a
tube. That's the stuff used to shield electrical contacts in automobile connectors from moisture and oxidation.
I submitted both compounds to a series if tests, including concentrated HNO<sub>3</sub>,
H<sub>2</sub>SO<sub>4</sub>, HCl, NaOH and a few solvents like Heptane and Isopropanol and it didn't react to any of them. I
tested both greases on the ground glass surface of my dessicator under vacuum and it didn't try to creep off or suck in. Both compounds are remarkably
similar. So far, the only difference is the outrageous price of the laboratory grease...
I'm always baffled by the price of labware and equipment from the official big-name lab suppliers... How do they get away with such outrageous prices?
Maybe that's why meds from big pharmaceuticals are so stupidly expensive.
P.S. Sigmhumm-Aldrhumm sells the dessicator in the pic above for something like $600. I paid $25 for it, including a one-pound bottle of blue
drierite!
So in conclusion, if you want to save a few bucks on vacuum grease, in Canada, go to Canadian Tire, or in the US to your local NAPA auto parts store
and get the silicon dielectric compound!
Robert
--- Art is making something out of nothing and selling it. - Frank Zappa ---
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trb456
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How to best use RZ2.5 Rotary
Reading over all the great information on vacuum pumps here and elsewhere, I think I made a vacuum pump mistake, and I'd appreciate some assistance in
how to optimize my situation.
I purchased a Brandtech RZ2.5 rotary vane pump, which is a very nice piece of equipment, but perhaps not optiimal for chemistry. So far, I have been
unable to prevent emulsifying the pump oil, which I understand means water vapor and general badness. I changed the original oil, and after running
the pump, the new oil eventually clears and still looks very clean (I can see through to the fixtures in the chamber). I'm only running the pump
about 5 minutes at a time for testing. In my last test, I used a cold trap in cold water (iced with salt--I'm not ready for liquid nitrogen), and the
cold trap did have some condensation, but clearly not enough to prevent the white oil. It seems, based upon my limited reading, that this type of
pump would prefer an inert gas, which I am not ready to provide.
I have ordered a separator for this pump, so perhaps this will help. I can also add a pre-trap before the cold trap. But I'm not certain this can
eliminate all water vapor. Is the answer to simply change the oil after an extensive vacuum application? If so, what amount of time is "extensive"?
Or does anyone have any other tricks of the trade that may help?
Thanks in advance,
trb456
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watson.fawkes
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| Quote: Originally posted by trb456 | | So far, I have been unable to prevent emulsifying the pump oil, which I understand means water vapor and general badness. [...] In my last test, I
used a cold trap in cold water (iced with salt--I'm not ready for liquid nitrogen), and the cold trap did have some condensation, but clearly not
enough to prevent the white oil. It seems, based upon my limited reading, that this type of pump would prefer an inert gas, which I am not ready to
provide. |
If you can't trap it and can't filter it, it's going to end up going through the pump. Exercise:
What's the vapor pressure of water at the ice+salt temperature you were using? There's a reason that people use LN2 traps, after all. You'll do much
better with dry ice (+ heat transfer medium like acetone) to start with. Also: concentrated H2SO4 can be used to extract water vapor via a trap
column; this needs another trap in line after it to capture aerosol droplets of acid.
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trb456
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Thanks very much for the reply, w.f . I was thinking similar things to your proposed solutions, namely a second trap and colder trap. I'll do some
more testing and see how it goes.
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chemrox
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I hate anything that requires flash. Adobe doesn't bother to keep up. Mac-like arrogance.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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