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aonomus
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Chances are what I will do is bend some sheet aluminum (or just sheet metal) into L's with notches on the top/bottom, then ziptie/worm gear clamp them
onto the casing with thermal goop. I already have a fan aimed at the casing which helps control temperatures somewhat, I'll report back with results
when they mean something.
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peach
Bon Vivant
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I've just been trying to recheck the gauge I have again against the pump out of it's case. The gauge is almost certainly skewed as it approaches zero.
If my boiling point is correct, it's running at something more like 26mBar.
I also noted that the dial was now reading a little higher than before even with only it connected after the distillations. I tried
reapplying some more grease and saw it fall a little again.
That means the thicker grease outside the can idea isn't going to work, at least at the speed it's running (which is likely way quicker than it needs
to be to maintain the vacuum; the glass isn't leaking anywhere near 0.2CFM); it's running out of the chamber too quickly.
Options remaining, use a significantly thicker oil (heavy motor grade?) and simply squirt it into the can. Slow the piston down with a variac or step
down perhaps.
I suspected that gauge was up to no good, and have seen numerous guys on youtube mentioning strange skewing effects around zero with the mechanicals.
I can't triple check it without the hot gauge behaving. Aonomus, are you set up to distill things? If so, have a go with some distilled water (or
anything else you can get as a solid reference) and see how that rotary is managing.
If I can find some heavy oil in the garage, I'll give that a whirl too.
[Edited on 14-9-2010 by peach]
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aonomus
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I have the glassware, just not the time. Being gainfully employed can also be quite the detractor to tinkering....
I'll give it a shot trying to do vac. distillation after I make a makeshift drying tube using plumbing parts and CaCl2 prills probably on the weekend,
maybe sooner.... I managed to break both my crappy vac. gauges, so it will be hard for me to determine what the vacuum is.
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peach
Bon Vivant
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Nooooo, I mean, check the vacuum using a distillation.
If you distill something that you know is next to pure (preferably something with a BP over 200C), the temperature it comes over under vacuum can go
through a nomograph to tell you the pressure.
And you can check things like your thermometer against a known standard, boiling distilled water and ice made from the same
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spong
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Connecting the tube straight to the air inlet is a great idea peach  I might
have to try that and then reseal the can so the oil can still flow around, I wouldn't have to worry about sucking solvents and water through it then.
I have a fridge pump question though...
I got one from uni today, they were throwing out some fridges and freezers from the biochem building, I couldn't help myself. I got it home and opened
it up to wire the plug on and realized the capacitor isn't there  I doubt I'd be
able to get it either without tearing the whole thing apart. There was the power cord which led into the little box on the side of it and a white cord
that ran out into the fridge somewhere. The white cord had 4 wires, one earth, one white, brown and blue. the brown and white both connect to the
relay I think it is in different spots and the blue attaches to the motor protector along with a wire from mains.
Here's photos, they'd explain it better than me. I was wanting to put the cap from my old compressor onto this one but don't know which two wires to
use.
Hopefully I can get this running, I was wandering around the building and saw a few -80C freezers, if this was one of those then I'd have a pretty
hefty pump
[Edited on 17-9-2010 by spong]
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Contrabasso
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Well my target with fridge pomp vac distillation was(is still!) to distil off nitric acid at something like 60C rather than 80C so that there is still
an easy condensation task but a lower amount of red fume made and dissolved. Quite simply bleeding air into the vac line with a needle valve to hit a
boil at 60c will do for me. I don't care what the pressure/vacuum is just I want clean WFNA at 1.50x SG
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aonomus
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I just tried a vacuum distillation with water; as soon as I applied vacuum the water started to boil and my max achieved pressure was at 20degC vapor
temp, maxing out at 23degC when it really got going (bumping and boiling fast). My condenser water was simply too warm (read: 15degC), so I did end up
sucking alot of water into the pump. I ran it for an extra hour and I hope I got all the water out of it.
Using a nomograph, 20-23degC works out to about 40-50mmHg, not as strong as I'd hoped, but that was limited by the vapor pressure of water. If I were
to try to distill something like phosphoric or sulfuric acid, I'm sure I could get the pressure even further down.
I think this pump is overkill for vacuum filtrations (read: flask implosion!?) but good for distillations.
Oh, and with the cooling fan I rigged up blowing against the casing (no heatsinking or anything, just the bare painted steel case), external
temperature was about 40degC average for the 30 minute run. I suppose enough water got sucked in to help cool it down, as the water started to
evaporate, taking heat with it.
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Magpie
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I'm confused as to how you measured your vacuum. If using water I would start out with the water as cold as possible, letting it warm to room
temperature slowly under your pump's vacuum. When the water starts to boil I would shut down the pump and measure the water temperature. Then go to
a vapor pressure table or graph (vapor pressure vs temperature) and look up the vapor pressure corresponding to the temperature you measured. This
vapor pressure is the pressure of your vacuum chamber. I don't see any need for a nomograph.
If this is what you did, then I just didn't understand.
The single most important condition for a successful synthesis is good mixing - Nicodem
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aonomus
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My basement is pretty darn cold, initial temp of the water was around 8-10degC, RT was 19. I placed the flask in a water bath at 20degC and applied
vacuum. On boiling, water temperature was 20degC, as was the vapor. Once the boiling subsided, heat was applied to the water bath, and boiling
resumed, with temperature at 23degC constant.
Looks like by vapor pressure ( P = e(20.386-5132/T) ), pressure was around 17-20mmHg (I'm giving this a bit of range for error).
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peach
Bon Vivant
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You definitely want to ignore what the liquid does at first, it'll almost always start to boil, or at least de-gas, as soon as the vacuum is applied,
then stop. Temperature measurements at that stage are fairly useless.
I tried checking mine with eugenol, because it normally boils at somewhere around 250C and I knew the oil was relatively pure, meaning it'll distort
the measurements less at low pressures. The glass had also just been given a very good clean and the thermometer is a pricey mercury one from Germany
made to a BS standard.
Your 17-20mmHg translates to 22.5-26.5mBar, about what I was getting with the fridge pump out of it's casing.
I suspect, even with a cold basement, that water may be skewing the pressure the rotary can achieve. You may need to give it another go with some
reasonably pure, high BP oil and ice around the receiver. Also, try measuring the amount of material going in and coming back out at the start and end
of the distillation (with a pipette or scale that will give some level of accuracy given the volume / mass used), to tell you if any has buggered off
during the process.
I've tried distilling things like cyclohexane (ATM BP ~80C I think) under fridge pump vacuum. Even with my coil condenser cooled with ice, a
remarkable amount has 'disappeared' when it comes to checking the results.
{edit}I have a PDF in the works where I've plotted various methods of weighing against the recently calibrated 0.1mg balance I have access to. I've
tried those nasty looking £8.99 0.01g weed dealer scales from China, the digital ones for the kitchen, splitting piles of table salt by eye, using
rulers over pens as balance beams and using randomly selected coins out of my pocket as reference masses. The nasty looking £8.99 are keeping a less
than 1% error up to about 50g, despite me spilling agar and all kinds of crap over them, overloading them and never calibrating them. The kitchen ones
have a huge amount of error in that region, but that then drops to about 1% over 100g. Stacks of coins can also produce a reference mass with
vanishingly low errors as the error goes positive and negative over the years by an equal amount, so stacks of them cancel each elements error.
Amusingly, I can see the mint tweaking the presses as the mass of the coins changes over the years. There is a very stable, periodic sine wave
pattern.{/edit}
@sponge bob square panties
Try starting it without the cap, a lot of them work fine without it. If that fails, I'll double check mine (or check it anyway if I remember next time
I'm beside it). I currently have so much to do it's becoming tricky to keep up with it all.
Print, colour in.... "I know I've gone outside the lines, but that's okay,
because I like bein' myself"
[Edited on 18-9-2010 by peach]
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spong
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Yeah hopefully it would work without it, which pins should I wire the mains power onto? There's three, one of them would be the starting coil wouldn't
it? I might have a rummage around that dumpster again on Monday and see if I can pull the cap out, there was some glassware in it too but most of it
was broken.
I tried testing my pump out with the water boiling method, 34C, 50mbar... Not too good.
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aonomus
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I think that while my pump vacuum is high, its useless for low boiling stuff unless I can cool my condenser down way below RT using some sort of
refrigeration system (that is pretty hardcore).
That might even be my next project, convert some sort of refrigeration system into a recirculating chiller.
Or just get a cheap chest freezer, pop a few holes in the side, add a large reservoir and allow it to cool before starting a distillation.
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peach
Bon Vivant
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50mBar isn't that bad, it's still going to cause problems trying to distill solvents without some serious cooling on the go, and it's low enough to
drop the high boiling oils down towards hot water bath temperatures.
I'll have a look at my fridge victims next time I go down (not long). Telepathetically send me "check the wires" waves.
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psychokinetic
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Peach, would a fridge pump be able to get to such a vacuum that spongebob squarepants would expand to fill a 20L jug?
Would he survive?
Would he go back to his normal shape, or be forever known as Spongebob Flaccidpants?
“If Edison had a needle to find in a haystack, he would proceed at once with the diligence of the bee to examine straw after straw until he found
the object of his search.
I was a sorry witness of such doings, knowing that a little theory and calculation would have saved him ninety per cent of his labor.”
-Tesla
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watson.fawkes
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I believe that Mr. Squarepants is an open-cell foam, and therefore no.
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starch
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peach thank you for this amazing thread
you have really cleared a lot of questions up for me
thank you very much indeed
take care
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peach
Bon Vivant
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Quote: Originally posted by aonomus  | | I think that while my pump vacuum is high, its useless for low boiling stuff unless I can cool my condenser down way below RT using some sort of
refrigeration system (that is pretty hardcore). |
I've been watching the rest of your youtube videos and love them. A lot of them are virtually identical to what I'm interested in or thinking of, the
magnets in fingers, syringe pumps, arduino's, axel f. 
Shame we don't live a bit closer.
In terms of the pressure problems, you can simply bleed a bit of atmosphere into the system at the intake of the pump to raise the pressure.
I'm working on some things you may be interested in. I stuck a pressure and vacuum gauge on a 60ml BD Plastipak and measured a peak of 100psi+ when
squeezing it with my hands, before the tiny length of vacuum hose I was using to connect them with started to balloon out. The pressure sits still for
a long while, but is slowly dropping on the one I'm leaving clamped (it looks like it's leaking round the seal). I'll report back on where it finally
stays put and may try solvents (which would encourage the seal to swell and block the pressure in better).
Sticking the vacuum gauge on there, it can drop the pressure by 9/10th's of an ATM with one pull of the plunger. I don't have a one way valve handy to
try lots of pulls.
I'm wondering about pumping solvent, noble gases, reactive gases, circulating jackets, running higher pressure reactions, arranging three in a rotary
setup and driving them with a geared microwave turntable motor, using them for flash chromatography and so on. All of which I'm sure you could apply
your Arduino talents to or produce something useful with. E.g. use a length of black iron pipe & some caps to hold the syringe and force the
plunger down with a stepper. I'm still having major problems getting into microcontrollers. I've tried, multiple times, and am now reading John's book
on the MSP430, since I have one. I am worried about picking up an Arduino in case it teaches me to program in a manner too reliant on the compiler and
someone else's work; which may scupper my plans down line.
I also put the gauge on a fridge compressor and read 600 - 800psi, mainly towards 800. The nomograph result I got for redistilling some 250C oil under
vacuum, run in reverse, would suggest something like 550psi. Either way, it's worryingly high and I won't stand in the same room as it at this early
stage of things (that's saying something considering what else I get up to, minus gloves, masks or goggles).
| Quote: Originally posted by Magpie | I'm confused as to how you measured your vacuum. If using water I would start out with the water as cold as possible, letting it warm to room
temperature slowly under your pump's vacuum. When the water starts to boil I would shut down the pump and measure the water temperature. Then go to
a vapor pressure table or graph (vapor pressure vs temperature) and look up the vapor pressure corresponding to the temperature you measured. This
vapor pressure is the pressure of your vacuum chamber. I don't see any need for a nomograph.
If this is what you did, then I just didn't understand. |
That will work, but redistilling a suitable amount of a high boiler is going to produce a more stable, applicable to another distillation, result. And
distillations is the main aim of the game for most people.
When you shut the pump off on that, oil will start to back stream, so you'd need a tap (I'm guessing this is what you mean). Also, even with the tap
in place, the temperature will skew as the solution continues to boil in a now enclosed volume.
You shouldn't be using water, or anything that boils near it, for these tests really. All of these pumps, aspirators included, will reduce the
pressure low enough that enough will boil off from the receiving flask to skew the pressure you finally work out. If it boils below water, even ice
cooling the receiver won't work.
Hence my recommendation of a reasonably pure, high boiling oil for the test; if you want to see how low it can theoretically go. That's not entirely
necessary for a lot of chemistry work, but it is for checking the maximums the pumps can do under the best circumstances. And it's important when
distilling high BP oils, which is when a vacuum is really needed.
| Quote: Originally posted by psychokinetic | Peach, would a fridge pump be able to get to such a vacuum that spongebob squarepants would expand to fill a 20L jug?
Would he survive?
Would he go back to his normal shape, or be forever known as Spongebob Flaccidpants? |
Squarepants lives under the sea. He'd burst on land, or suffer some form of major brain hemorrhage and clotting issues (he probably has already, so
that's not going to help at all).
| Quote: Originally posted by spong | Yeah hopefully it would work without it, which pins should I wire the mains power onto? There's three, one of them would be the starting coil wouldn't
it? I might have a rummage around that dumpster again on Monday and see if I can pull the cap out, there was some glassware in it too but most of it
was broken.
I tried testing my pump out with the water boiling method, 34C, 50mbar... Not too good. |
I might have missed something, but how did you test it if it's not wired to anything? Unless you mean a different pump? 
Those pins shouldn't be wired direct to the mains. The pump will almost certainly sit there going "Hummmmm" if you do, then it'll burn out and need to
go in the bin.
You need to push that starting relay back on there.
This reminds me of aerogel. I've been reading into making that, it looks like fun. Particularly if I can sort out molding it into solid forms as
opposed to the gravel United Nuclear sells. That's got to make one brutally compact furnace.
| Quote: Originally posted by starch | peach thank you for this amazing thread
you have really cleared a lot of questions up for me
thank you very much indeed
take care |
No problems. The biggest thank you would be for you to start making some similar videos. Too much sitting around knowing things and not telling anyone
until they make a mistake, then pouncing and saying 'har har' goes on in forums I feel.
[Edited on 21-9-2010 by peach]
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aonomus
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| Quote: | | Shame we don't live closer |
Canada still respects the Queen for some reason, is that close enough?
| Quote: | | In terms of the pressure problems, you can simply bleed a bit of atmosphere into the system at the intake of the pump to raise the pressure.
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I have a needle valve I managed to get from a welding shop that was used, needed a little bit of cleaning on the inside, but the valve seat was still
clean and working.
@peach: shoot me a U2U and we can chat off-board (more convenient perhaps).
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food
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Hi, great work dude; maybe you're tired of hearing that by now. Really though. I've been curious about fridge pumps for a while now, but been put off
by what I'd been hearing and reading. Even at an appliance repair shop the fellow told me, 'oh, it will just burn out'. You're videos have answered a
bunch of questions, and anticipated even more.
I didn't do more than test the pump in the photo that I've (hopefully) attached, but everything that I'd read about overheating prompted me to wind
hose around and against the pump body in a preemptive mickey mouse attempt at cooling. So I find your reports quite encouraging.
I may be back. Politely asking questions. Cheers
(edit; don't know why I can't see the attached pic; will return to this later)
[Edited on 25-9-2010 by food]
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Contrabasso
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Airflow needle valve came from a pet shop (fish tank section) for £2.99 and it's nominally waterproof!
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peach
Bon Vivant
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No, it's seriously fine, continue telling me how nice I am. Presents, kisses and monetary donations are especially welcome.
The overheating thing, anomonus has demonstrated, is a big divide between the US and Europe.
In the US, a lot of guys seem to be using those rotary things from AC units. And his was absolutely roasting in no time.
The piston kind, the little humming black boxes in the backs of kitchen fridges / freezers, they don't seem to have any major heat issues. I've never
used a fan on one, and run them for half a day solid, or more. They do get fresh cup of tea hot, but a fan from a computer fan will sort that if
you're worried about it.
I have now gone fridge pump cracky, and have been coming up with all kinds of ideas I want to try with them (decent vacuum, 500psi+ positive pressures
and they're free, there's lot of things they could potentially do). So there may be more unusual things on the way. I would have put some more up by
now, but an item I need has mysteriously gone missing (that kind of missing where you put it down, turn around, turn back and it's gone for two
weeks).
I was hoping there'd be some easy way to drop the temperatures even more, but the laboratory super freezers (I've now discovered) are genuinely quite
complicated. They use one pump to cool the other. But that's not still out of the question, since I haven't read into it enough (e.g. stick one
freezer inside another).
I've also been looking at how syringes perform, the big, wash your horse's nasty cut out, disposable kind. They can be used to generate reactive gases
for tests or producing small batches of things. And they don't pop until at least over 100psi.
I think they're polypropylene, which is fine around cyclohexane. One of the key solvents for chromatography. Combined with a suitable polar solvent,
they could make a very cheap flash chromatography setup. The current industry innovation in flash is mid pressure, ~150psi. Some domain as the
syringes can manage.
Feel free to ask away. The reason I started this thread was to finally clump all the fridge questions in one place, get them answered and move on.
Because every forum I've ever visited about science is stuck in neutral with the fridge pump questions.
[Edited on 26-9-2010 by peach]
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aonomus
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So an update: under vacuum, continual operation (1h+ filtering fine metal hydroxides), and with a fan pointed at the pump, I get about 40-50degC, the
fan really does help alot. Additionally, getting the motor up to full speed helps alot with the heating issues.
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hissingnoise
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| Quote: Originally posted by peach | | (that kind of missing where you put it down, turn around, turn back and it's gone for two weeks). |
Oh, right - the kind with two outcomes - 1) wife or SO finds missing item after search lasting 3 microseconds and 2) wife busy (cooking or
shopping or whatever), so distressed hobbyist freaks out using foul language in loud voice thereby pissing off said wife or SO; peace only being
restored in wee, small hours.
Know them well. . .
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Magpie
lab constructor
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| Quote: Originally posted by hissingnoise |
Oh, right - the kind with two outcomes - 1) wife or SO finds missing item after search lasting 3 microseconds and 2) wife busy (cooking or
shopping or whatever), so distressed hobbyist freaks out using foul language in loud voice thereby pissing off said wife or SO; peace only being
restored in wee, small hours.
Know them well. . .
|
Recommendation for above:
1) Counsel wife or SO not to enter lab except by special invitation - for their own safety of course.
2) Kitchen utensils are to move in one direction only: from kitchen to lab, never the reverse.
The single most important condition for a successful synthesis is good mixing - Nicodem
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peach
Bon Vivant
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If I was going to be pessimistic, I might suggest things like that 'go missing' when they're tidying up.
I think I've mentioned this before, but I've never had any fire problems despite leaving solvent soaked cloths all over the place, it in the sink and
on me, whilst I sit around smoking or using a blow torch.
A 'fee-male' cat entered the scene not long ago and, for the first time in around a decade plus, within literally 30s, whooompf.... the surface is on
fire, the drain is on fire.... she's shitting her pants.
Reason, attempting to light a candle and then place it next to the used cloths.
When I was in my teens, I was trying to clean bia-tch-umen tar off the bathroom floor at one point, which had been used to stick the tiles down in the
days of old. I was sat, with the door closed, with the entire floor drenched in petrol and the can next to me. I turned around at one point to
discover, yes... ANOTHER CANDLE had been light nearby. My face was going numb by that point (after hours of the addictive petrol smell), yet even I
was still coherent enough to realize that might be a poor choice of time to light a candle, in the middle of the day.
Not long after, that incident, I came home to discover my mum had set the curtains on fire (and they were still on fire). Cause.... candle.
Girls + letting THEM light the candles.... bad, bad, combination. That's probably why their hearts melt when they discover a pro has done it for them.
Star Trek votes pro for domestic violence (upskirt cam);
Anyway, I'm STILL looking for this thing.
I always thought, if God does exist, I'm probably getting stuck in limbo for a few centuries when I die. Where I'll eek out my time coming back as a
ghost, moving pens, pencils and other stationary items when they're needed.
"It looks like you're writing a letter, so I'm taking this pen"
[Edited on 26-9-2010 by peach]
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