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Author: Subject: LET THIS SIGNAL THE END OF THE FRIDGE PUMP QUESTIONS!
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[*] posted on 26-9-2010 at 20:44


How about oil from the output? Were you saying in one of the videos that you weren't seeing any?

I just powered up one of the pumps that I've scavenged (it's a piston type fridge pump; looks like what you're using). I'm seeing something from the out tube. You can feel a faint something on your fingers in the output stream, and a piece of tissue shows something after a few seconds. Unless that might be residual traces of refrigerant coming out the oil? It's only been run out of the fridge for an hour or so. I do have the tube aloft, above the pump.

I anticipated getting some kind of a filter on that if the pump is otherwise usable.

Got a kick out your elastic band ball. I cadge elastics directly from our postie regularly. He's a bit more 'enviromentally conscious'; many of them just drop them on the pavement.

pump_1.jpg - 280kB

ok, cool, got the snap up; my nice elastic bands, oh, and a pump. I've not been running it like this, I jerry rigged the cooling hose after all the alarmist overheating info that I'd read (or misunderstood)

as shown, the kitchen/lab tool migration has been eliminated by merging the two locations
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[*] posted on 27-9-2010 at 11:46


I see what looks like 115V written on the side of that, meaning you may be in the US right? If so, that may be one of those rotary type ones anonononmus was talking about, which is much more likely to spit oil out. You can hear in his video that they make quite a lot of noise at atmospheric pressure. Where as the piston kinds make very little and pretty much go silent under vacuum (to the point that people think they're stopped running).

Try putting a glass cup over the exhaust and cling filming the top over, then let it run for a while. If there's a serious oil problem, you'll see droplets on the walls, or a puddle at the bottom.

If it's a piston kind, that may just mean it's settling and has gotten some oil in the pump head when you started moving it. If it keeps doing it, you'll want some form of oil capture on the exhaust if it's going to be running at or near atmosphere for ages.

I just noticed on a very new piston pump I removed, the tiny expansion bulb is packed with something. I haven't cut it open but, if I shake it, I can hear something that sounds like little pellets or beads in there (about 2-3mm big judging by the sound and the fact they won't pour out of the tubing attached). I wouldn't be surprised if those are just little chips of metal to catch any oil mist and send it back.

The oil capturing thing doesn't need to be complicated, a bit of copper tubing (from a bin / skip) soldered on there and filled with something suitable (glass beads, BB's, lots of tiny springs, swarf / chips from a lathe, wire wool) will give the mist somewhere to collect and drip back down from.

I had a gigantic Alcatel pump at one point, which would usually be £2k+, and the oil trap on the exhaust was just a tube with a big spring in it.

When the pump is under vacuum, the misting should drop WAAAAY down to practically zero. It's the gas flowing through that's blowing the oil out. With no (or next to no) gas going through, there's nothing to blow it anymore.

Lots of the references for using these fridge pumps come from the guys using them in the opposite direction, to give positive pressure for airbrushes, spray guns and the like. They're using them in a way where oil will be hugely encouraged to leave the pump because they're running around atmosphere so much of the time.

If you're worried about the oil level dropping, chop the end off that oil fill line on the top left in the picture and you can squirt some more in with a syringe, no problems.

I like the cooling setup happening there. You didn't ever work palletizing boxes did you? I did. 12h shift on my feet continually, and an hours bus ride each way. The sound of the factory never left my brain, even as I tried to fall asleep.

[Edited on 27-9-2010 by peach]




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[*] posted on 27-9-2010 at 14:49


I'm in western Canada, not far from where Fraser empties into the Strait of Georgia.

I'll take your suggestion with the cup, see what happens.

As far as the pump, I'd be surprised if it's not the piston type. Everything that I've seen so far, without doing pump surgery, indicates: piston. It's dead quiet. Like you say, you could miss that it's even running.

Not so much concerned about losing oil as breathing it, or air-brushing the room with it:)

You're a psychic ! I did work crating and/or palleting boilers and furnaces for a (brief) time. At that time I don't think that saran wrap type products had made their appearance in the shipping department. In an unguarded moment the air powered wood stapler came to rest on my boot and drove a 2 inch staple through one of my toes, straddling the bone. Ahhhh, happy memories!
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[*] posted on 27-9-2010 at 16:27


If it's super quiet, it's almost certainly a piston one yep.

Try letting it run for a while. It might just be that some oil as splashed up the intakes inside.

Tell you what, if that level of oil mist worries you, never buy a lab rotary. The room looks like a rainy cloud has taken up residence about after about two minutes at atmospheric.

I'm not psychic, I can simply see the force flowing within the wrapping, the Jedi signature. Even if cling film wasn't around then, it's omnipresent nature seems to have become part of your packing soul afterwards.

I got really pissed off at one point and the machines were permanently set to run slightly quicker than the humans could pack, so packing ran at maximum speed and there'd be a pile to get on with when something went wrong. I packed one pallet with all the boxes sticking out at wonky angles and then everyone got upset (the pallet came back). They even had hourly graphs of packing performance up in the washing 'airlock' to encourage line to line competition. Bastards.




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[*] posted on 28-9-2010 at 16:41


After a big google push searching discharge and oil mist filters it finally dawned on me that draping a hose out the window is an option too. We'll see.

I do have an ancient Edwards ES100. I traded labour for it. I got a pdf from absolutevacuum.co.uk, and a manual from the interweb. I've not done more than run it up. It's a beast alright, very noisy, oily etc. I think that it may benefit from a tune-up. The manual is a treat; 'Care and Maintenance Manual' for ES and ED 35, 75, 150, and 250, and ED500. I could upload that if there is interest (18M).

That job sounds .. special. Like a Charlie Chaplin movie. That's my polite take on it; good that you managed to escape.

Cheers
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[*] posted on 28-9-2010 at 17:34


I've taken an Edwards to bits.

The complexity of doing it depends on how good you are with your hands. It's either going to end up a.) broken b.) fine

If you have experience machining things (know what a surface grinder is etc), welding, are good at DIY'ing, you'll probably be okay with it.

Taking them to bits and changing the oil doesn't always increase the vacuum. And the vacuum degrades quite drastically on them as so much starts leaking / boiling at their maximum vacuum. If the vacuum level is poor, try degassing the oil first, as there may simply be something dissolved in it (like a solvent or other volatile). The degassing can take a good while. Block the intake and leave it running, checking the pressure every half hour or so. If it keeps falling once it's hot, there's probably something in the oil (water is a good possibility). Leave it going until the reading sits still. The manufacturers claim 0.001mbar, but the reality is, most of them are floating around 0.05 to 0.1mbar after they've been used a bit; particularly if you're not super duper careful with them. Easily enough for distillations (too much in fact), but that theoretical factory rating doesn't last all that long outside of the physics labs (where they spend their lives sucking down chambers full of dry, noble gases).

It's also reaching into the pressure ranges where simple push fit rubber hose connection leak enough to distort the pressures if they're not tight and left alone. I can see the vacuum changing if I lean on the hose. Which is why they have those compression flanges on them and use bellowed pipes that don't bend so easily. At the diffusion / turbo / ion pressures, the rubber in the seals begins to bleed, so they use discs of copper. The flanges have knife edges on them that pierce the copper and seal the flange. Then the disc goes in the bin when the chamber is opened.

On the subject of taking lab pumps to bits, the insides are usually a.) the same as a fridge pump in terms of casting and machining b.) if they're a few years old and have been run near anything damp (like the atmosphere), they'll look like a cake of rust inside, unlike a fridge pump (the pump head is usually cast iron and will rust in hours once the grease is off). The rust isn't an issue provided the mating surfaces are still good, which they universally should be if they've mated corrected. They're surface ground and have oil constantly trapped between them, so it's hard for water to even get in there once they're clamped together.

If you take it apart, have a big tray / box next to you and expect oil everywhere. As every single part comes out, drop it into a cup for that section and put it in the box. Some of the bits are tiny and essential. Fire up the digital camera and take lots of photos in case you forget where things go.

I've also bought things from absolute vacuum before. I can tell you right now, that picture of a military jet on their logo does quite an injustice to their service. Which is piss poor by normal standards. I'm still waiting for a reply from them, week two later, and they have my money.

If I call them, they tell me to email them. If I email them, they don't reply. They're selling used vacuum pumps, not nuclear bombs ffs.

[Edited on 29-9-2010 by peach]




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[*] posted on 28-9-2010 at 18:19


For a while I was itching to get the thing in pieces. I didn't do that yet. A whole bunch of reasons.

To mate a hose to the vacuum input I found a suitable plastic barb and siliconed it in. Well that works, how well I'm not sure. I ran it with the input closed and the ballast open for an hour, maybe longer. Didn't seem to make that much difference. Not changed the oil yet, didn't want to spend the money. I'd been expecting a fiercer vacuum from this item, it is after all a 'high vacuum' device. (disclaimer: these forays into vacuum pumps are something new for me; don't have much related background to draw on)

I was thinking, well, maybe the vanes are worn or deteriorated, which might affect the performance.

I'll be giving it some attention at some point.

It would be nice to have a guage to check pressure. I came across a suggestion on a hobby site today that mentioned vacuum fuel pressure guages from auto stores. Don't have much cash to throw at this right now. At around $15 canadian sounds too good to be true, but maybe handy for not-so-low-pressures?

Disappointed to hear about your absolute vacuum experience. My illusions lie shattered. I had been suitably impressed the way that they got right back to me with that pdf. I got an email from them yesterday, oddly enough. 'dear customer, we're moving, this is our new address', that type of thing. Maybe the move has buggered up their response time.

Cheers




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[*] posted on 28-9-2010 at 18:49


Silicon seals will work fine at distillation pressures, don't stress. I've checked it, they do. So will epoxy glue. You just need to be sure it's not on a connection that'll be routinely knocked around and bent.

As I show in one of the videos, I can put my hand over the intake on the rotary pump (below 1mbar) and it's fine (I've seen a guy doing it with a 40CFM rotary with a roots blower on top of that). You can't judge the vacuum that way as an absolute vacuum is only ever -atmospheric, not -200bar. You'd have a far, far worse time trying to inhale off a freshly filled cylinder of nitrogen. About 200x worse.

Neither is a $15 auto guage going to get even close to accurate on rotary pressures. I have a fairly expensive mechanical gauge that you see in some of those videos, it still can't deal with it.

This is where vacuums start getting expensive. Sub 100mbar and down below 1mbar, you need expensive gauges. Look for mechanicals that start at 100mbar (1/10th atmospheric) if you're going the mechanical route, not 1000mbar (atmospheric). 1/10th atm is where volatiles start boiling around room temperature, and where high BP oils boil at water bath temperatures (you should be using a foil TP, not baths).

Also in those videos, you see the fridge pumps and aspirators are right down near the outer space line compared atmospheric pressure. It's a massive leap for the gauge to make, trying to read accurately in the last 1% of it's range.

Physics labs will usually have quite a few different, very expensive, gauges on a chamber, involving things like Iridium (a platinum group metal). And they'll break if switched on at the wrong time.

Auto gauges are designed to deal with atmosphere to the turbo pressures. And a turbo in a car is no where near the turbo in a physics lab.

This is why I go on a big anti-rotary campaign a lot of the time. Under those pressures, the solvents boil too low to capture, the pumps costs a lot, maintaining them costs a lot and the gauges are expensive. And using them for a solvent boil off is the wrong idea in the first place if you don't have liquid nitrogen in the condenser. Even dry ice isn't cold enough for solvents under rotary pressures. Then there are yet more problems. Liquid oxygen collecting in the condenser. Storing the cryogens, pumping them, the hazmat delivery on the cyrogens, the training needed to handle them. The cost rockets up into the thousands (new dual stage edwards $2k? controller $1k? trap $200+?, cryogenics $xlotsmorex, special vacuum taps $more). For what? Lots of TRULY unnecessary, counter productive zeros? Solvent in the pump? Even curly arrow has fallen into the trap, and other chem bloggers, of thinking a rotovap should go on the latest rotary pump. No. Even Buchi says no, and then charge you $1-2.5k for their pump, which works at fridge pump / cold aspirator pressures.

Talking about pressures, here's my thought for the day. Even in space, the maximum pressure differential is only 1 atm, 14psi. At the bottom of the Mariana trench in the sea, the pressure is about 16,000 psi with humans inside. That's not messing around!

Jelli-fishies in the Mariana trench (it's 6-7 miles down! :o and pitch black, at 16kpsi).


[Edited on 29-9-2010 by peach]




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[*] posted on 28-9-2010 at 21:12


LET THIS SIGNAL THE BEGINNING OF THE FRIDGE PUMP QUESTIONS!

alternate title

you make some good points, more in line with my economy as well

thanks

the rifters books are set in and around Mariana trench; free online for your reading pleasure



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[*] posted on 29-9-2010 at 09:08


Provided they're all in one thread from now on, that's cool also. It was having the splattered all over the forum and being repeated that wasn't helping.



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[*] posted on 29-9-2010 at 09:10


Provided they're all in one thread from now on, that's cool also. It was having the splattered all over the forum and being repeated that wasn't helping.



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[*] posted on 29-9-2010 at 11:34


Quote: Originally posted by peach  
Provided they're all in one thread from now on, that's cool also. It was having the splattered all over the forum and being repeated that wasn't helping.

Quote: Originally posted by peach  
It was having the splattered all over the forum and being repeated that wasn't helping.

Quote: Originally posted by peach  
being repeated that wasn't helping.

Quote: Originally posted by peach  
being repeated

Quote: Originally posted by peach  
repeated.


Nice one.







“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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[*] posted on 5-10-2010 at 17:21


ahoy ahoy

didn't want to get back to this before I'd actually done something with the pump

I did, I put together a very diy buchner funnel and used it to do some filtering. Worked super well. If anything it seemed I could have gotten by with less vacuum. Did I read something about using aquarium parts to bleed air into the system? It would be nice to be able to moderate the vacuum.

Also, peach, in one of your videos you mentioned getting quirky results once your pump was warmed up. That's getting ahead of things for what I'm doing, but if you have any comments about that it would be interesting.

I'm not going to worry about guages right now. No budget for it really. I did put some warm water into a flask and put the vacuum on it, after a few seconds it came to a boil. I have a few pieces of glassware, but no thermometer adapter.

Also putting the oil dispersion concerns on hold. Running it briefly to filter stuff it's not bothering me.

Meanwhile an idea for hose, when you don't have the right stuff: if you've got softer hose that your pump and the barbs on your glassware will accept, it can be stiffened with a very rigid, narrow white hose that the hardware stores carry (not sure what you'd call it, it's white and not transparent). Your pump and item-to-be-evacuated are connected with the softer hose, inside the softer hose you have a length of this very stiff, narrow hose running barb tip to barb tip. Kind of cheesy, but it work[s|ed].

Cheers
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[*] posted on 5-10-2010 at 18:06


My macgyver oil trap is simply a mineral oil plastic bottle (the same one used to store the old ester oil and used to contain the new mineral oil that the pump was flushed with) with a hose in the neck of the bottle and a few cotton balls jammed into the gap. They act like a good enough filter to be cheap yet knock down probably 99% of the oil fumes/water droplets. Plastic bottle also means no shattering risk under pressure.
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[*] posted on 5-10-2010 at 18:10


A long spring, or anything like that will do as well. In the UK PVC tubing is stiff enough it'll work, because it's quite a bit tougher when it's cold.

You can use anything to control the vacuum so long as it creates a controllable hole.

The quirky results thing, sometimes if I leave some of them on for hours, the pressure starts bouncing up and down a bit, which bumps the flask and the temperatures. I haven't tried it yet, but I suspect putting two in series will get rid of that.

The precise pressure isn't super important a lot of the time. If you're distilling something and you know it has a big percentage of some splittable component in it, you'll see it appear on the thermometer at some temperature. So long as the temperature sits still, it's doing what you want it to, distilling it without much oxygen around and at a significantly lower temperature.

Knowing the precise pressure is only important when you're trying to identify something using the boiling point as a piece of evidence. If you already know what it is and that there's lots there, that's not a problem.

Filtering things, the pressure is easily low enough. If it won't filter on a fridge pump, it probably won't do much better on a lab pump.

One of the main problems with filtering things as the paper or sinter starts to clog is that the pressure in the flask and around the filter drops really low. The solvent then boils and cools it's self to a near solid. So the filter element literally freezes up and zero will go through. That could actually happen worse with a lab pump, as the lower pressure isn't going to help pull things through much, but it will boil the solvents way below zero.

I've had some filtrations where it'll literally all day or days to get them through. The solution isn't high vacuum;

Wrap a super dry, fluffy towel around the vacuum flask, preferably all precooled. When the solvent tries to boil, it will rapidly stop as it can't pick up anymore heat to do so.

Stick a second hand, ultra cheap, adjustable hot air gun near the filter element and stem and gently warm them up.

That can get those same filtrations done in minutes.

If that fails, fire up the stirring. The very CAREFUL stirring. ;)




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[*] posted on 5-10-2010 at 18:29


@aonomus you mention 'new mineral oil', is that just to replace dirty oil or are you changing to different oil to improve performance?

@peach that's pretty funky that business with the solvent state change, I wouldn't have expected that. What's that about careful stirring as he final option, stirring what?
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[*] posted on 5-10-2010 at 19:44


The filter cake.

That is the last resort. If it's a paper filter, there's a good chance you'll rip the paper and dump your thus far hard won cake into the flask. Much swearing will follow. If it's a glass sinter, you'll damage the sinter and make cleaning it a whore of a job. Lots more swearing and possible alcohol problems as you deal with buying another funnel.

The solvent solidification thing is a bit unexpected and it took me a minute to work out what was going on when I first saw it happen. But it can stop a filtration dead, so there won't be a single drop coming through.

It starts happening when you're dealing with very fine, packable cakes and volatile solvents. Precipitates with a particle size around 10um or below are a good bet it's on the way. :P

It's also more prone to happen with sinter / frit funnels, because the cake will clog the entire surface the vacuum is trying to suck through, and effectively produce a stopper in the top of the flask. Solvent boils off in the sinter, the rest coming through solidifies. The problem snowballs too, well, iceballs. It starts, clogs a bit, makes it's self worse, cools more, clogs more, cools more and so on until it's solid.

Pretty much anything that forms visible grains or crystals, or only has a tiny amount of fine muck in it, will be fine though.

[Edited on 6-10-2010 by peach]




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[*] posted on 5-10-2010 at 19:51


Mineral oil was used to flush out the ester oil that the AC compressor contained. The ester oil is as the name implies, an ester of some carboxylic acid and alcohol. Water vapor will hydrolyze the ester oil and make it non-lubricating, causing wear on the pump and overheating. With the old ester oil it heated up far too much, but once I got it hot, and drained all the oil, flushed it with a few 100 mL of new mineral oil, drained that, and put in brand new mineral oil, it ran cooler and should be more resistant to water vapor causing corrosion to the pump.

Unfortunately the change in oil also means an decrease in the maximum achievable vacuum (vapor pressure limited), and that the mineral oil seems to really easily flow out of the pump, through the oil trap, and into the oil collecting bottle.
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[*] posted on 5-10-2010 at 20:19


With the inclusion of a drip tray, you could use the surplus to deep fry. I bet deep friend, freeze dried product is mighty greasy. All the better for my Atkins diet. :D



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[*] posted on 5-10-2010 at 20:38


Ok. The sinter/frit problems are luxuries that I don't have yet. My homemade funnel barely lasted through the job that I used it in before the disc buckled. I'm filing this away though. For future frozen filters. That and the heater-towel solution. Looking forward to cooling my own cakes at some point.

And solvent stripping. I'd been thinking that with a pump it would be that much easier to reclaim solvents. Only now seeing that the lower boiling point could turn out to be only one side of the coin, ie. recondensing the solvent might be an issue. We'll see.

As for the oil type, I've no idea what is in there now in the way of oil. When you said mineral oil do you mean the mineral oil that you'd buy in a drugstore, or are you referring to a mineral oil type of oil?
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[*] posted on 5-10-2010 at 20:52


I used USP mineral oil, but in general mineral oil refers to long chain alkanes. USP mineral oil is used as a laxative, lubricant, etc.

For solvent stripping, you'll either need an absurdly large surface area for condensation, and/or cold condensation surfaces. You'll find one or both of these in most rotovaps (water temperature varies, but even under strong vacuum a rotovap will still collect a good amount of solvent being removed without much trouble.
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[*] posted on 5-10-2010 at 21:43


thanks for the replies

that rotovap thing sounds cool

what part of the fridge do I salvage that from?

night

edit ooops, I was negligent when it came to reading through the beginning of this thread (I skipped right to the videos:)). Your compressor is a different type than mine. Mine is labeled R12 and if I'm understanding correctly uses a different oil. So these considerations don't apply. Please correct me if I'm wrong in this. Again, thanks and good night ~food edit

[Edited on 6-10-2010 by food]
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[*] posted on 6-10-2010 at 02:56


"15 pounds of yogurt!? I can't eat all that!"
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I've read A LOT of blogs and messages on the web, by people who have degrees in chemistry, about connecting rotovaps to dual stage rotaries and even high vacuum lines, which are sometimes running from diffusions elsewhere.

Then they complain about regulating the vacuum and the cold finger not being effective enough, so go out and buy yet more stuff to try and fix a mistake they've already paid a few thousand too much for; connecting the rotary / high vacuum line to it.

Nomograph.

Buchi's own line of pumps run around the pressure of a fridge pump / aspirator, but cost thousands.

Think about the quantity of handy gear the money for those over specified pumps could have bought if spent more carefully. Lots.

In terms of at home chemistry;

A fridge pump will get volatiles with a 100C BP at atmospheric pressure right down to the point where an ice cooled coil can have difficulty. You'll certainly want the receiver in a salt / ice bath if there's going to be a lot of solvent coming over, or it'll boil out of that too and through the pump; wasting solvent. I tried it without cooling the receiver and using cyclohexane on a fridge pump. About 80% of the solvent went missing.

Having dry ice and liquid around for home chemistry is fairly advanced stuff for most people, and a lot of effort. So ~20C is the minimum you'll want for an ice cooled condenser.

Even Buchi's running dry ice traps can struggle around those pressures, because they're pulling it off at a huge rate compared to a normal distillation, so it moves past the condenser quickly. Cold fingers, of coarse, have a pretty poor surface area by comparison with a double jacketed coil. So relying just on the temperature gradient is pushing one's luck.

The other option is nitrogen, liquid. Then those same chemists complain about oxygen collecting in the fingers and traps. Not realizing they can easily raise the BP to a number of specific temperatures, so it'll condense the acid gases but not fill the trap with liquid oxygen (which is quite likely to catch alight or explode depending on what else is in there).

Buchi rotovaps already cost a darn fortune considering something very similar can be achieved with glass that will do other tricks as well.

Add a rotary, and it's going to end up costing a whole lot more in terms of controllers, traps, cryogenics, taps etc. I mean, close to $10k. All to remove some solvent.

I can certainly see their uses for heavy use, intensive lab work where saving a few minutes is important. But I fear too many of the chemistry student coming through now will be far to used to the pull the handle and press go approach.

That would be okay, provided it worked every time and was cost effective. But with each rotovap sinking a good chunk of a member of the teaching staffs salary, and then sometimes pulling the solvent through to the pump or unacceptably bumping, that's a bit much.

There are also cheaper ways to build a rotovap than Buchi are using. I may give them a go at some point and challenge the Buchi empire.

[Edited on 6-10-2010 by peach]




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aonomus
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[*] posted on 6-10-2010 at 04:17


As a side issue, rotovaps exist that are fully self contained, computer controlled that vary the bath temperature and vacuum pressure (via variable speed diaphragm pump) specific to each solvent you are using (preprogrammed in). An example is the Ika RV10 (look on youtube, the video is like porn for chemists). TBH I've never had to go higher than 60degC on an air aspirator setup with my rotovap at work, but the air aspirator is fairly weak compared to a water aspirator, or, a vacuum pump.

A vacuum pump is only good if you know how to use it and you're not brute-forcing the problem by trying to max out the vacuum to strip solvent really really fast.
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peach
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[*] posted on 6-10-2010 at 05:44


Precisely.

And using an air aspirator is dead on, as the BP of most volatiles approachs 20C as the pressure get's to around 50mBar. Which is a warm water aspirator, fridge or diaphragm pump.

I just did a search for the RV10 videos on google and the first link I clicked, World News, had my videos on there. This is my 15 minutes of fame then, complete with a 6 year old girl's headband on.

That IKA is not as expensive as I was expecting it to be with all those motors and displays on there, but at $4k it's still a fair chunk of cash that would need you to be doing some intensive boil offs for it to be worth it.

I'm glad your guys at work have figured out that theirs will actually mong out if connected to a rotary or high vacuum line. As the majority of web based things I've read have been the opposite. Going straight onto some monster pump and then wondering why it keeps bumping like a jiggly girls ass on MTV, or why the pump oil is constantly filling with solvent.

I'd buy one for at home use if I could get hold of a rotovap cheap, but I'd spend money on more normal glass first (more beakers, stirring rods, weighing boats, blah blah blah). A rotovap is, of coarse, useless if you have nothing needing it's services. And a lot of the glass that produces things that then go into the rotovap will also evaporate solvents very quickly.

It's all down to evaporation speed alone. So the savings in evaporation time have to balance out the massive capital cost for it to be worthwhile. I can empty a 500ml flask in not a lot of time just with a stir bar and hotplate. In a uni lab were you have 30 guys all trying to run things through, the extra minute or two is important. At home, hmmmmmmm, questionable at $4k.

I saw a funny TV show from the US, a cookery one. Expecting to see hand whisks and folding spoons, to my surprise, he had a brand new Buchi sat on the worktop.

That's not an ice cream machine. :P

I know they do food science at school, but that's taking things a bit far.




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