Sciencemadness Discussion Board


IrC - 26-12-2010 at 16:36

Decided a topic is warranted for this subject. Anything related is on topic, whether hardware, materials, glues, pumps, links, or you name it.

Just a few links for some interesting reading and one for a seller of various gauges. On the subject from another thread I must add my Plexiglas problems were insurmountable. I was buying it from various local hardware stores. Several attempts and every time I had problems with cracking with the slightest pressure, and epoxy failing to adhere. I am convinced this is due to the formulation and/or manufacturing of the Plexiglas now coming from China. I used 3/4" fiberboard as a backing to eliminate problems with warping and several sheets glued together to reach about an inch in thickness (~1.75" total). Same cracking and glue not adhering problems each time. Out of desperation (and a wasted $140), I sacked an old plating bath vessel for some sheets of 30 odd year old Plexiglas. Worked perfect, after curing no leaks and zero cracks from the hardware which bolts the stack of sheets (also glued each layer) together. I would be interested in anyone's opinion on this.

Edit to add: also on topic are projects using vacuum so if you are doing high energy research or something else entirely by all means show and tell. I could not decide if this topic should be here or in technical so no problems if mods move it. While constructing vacuum setups is why I chose this section I believe often we learn new ideas to apply in building a setup by learning in detail about projects using vacuum (even distillation work) where problems were encountered by studying the methods used to overcome said problems. Possibly I am being too broad yet I see no other way to cover everything if we limit ourselves too a narrow spectrum of discussion.

[Edited on 12-27-2010 by IrC]

watson.fawkes - 26-12-2010 at 18:06

Gettering and Ion Pumping. This article is available at; articles are variously in English and Italian.

User - 27-12-2010 at 06:06

Well in that case :)

I am wondering if anyone has ever improvised things such a kickback flasks ,washing bottles, oil pump exhausts/filters ?
Currently I'm designing a system for my lab and some good suggestions are very welcome.

IrC - 28-12-2010 at 10:26

This is the next pump I added to my vacuum station, around a grand used rebuilt, good to 0.1 micron. So I have a single stage rotary for rough to around 70 microns, a new 2 stage to one micron, and If I can work the plumbing out I will add the 0.1 micron Alcatel. It runs very quietly. For now I think I will just clean it and do an oil change, test it to see how well it does. Will take some plumbing work to keep a nice short, large diameter route into the base of my bell jar platform but worth it. Best I could do before this one was around 1 micron. This hobby is expensive, a grand to move the decimal point by one place from 1 to 0.1.

The Alcatel only had a few days worth of run time with the oil kept clean by changing, then was stored for a few years. Kind of wondering if I should buy the rebuild kit before I start using it because it was stored (but never run) in a desert sandy location. Every time I went to that storage room sand was across the floor from blowing in under the door. I worry that there could be microscopic particles of sand in there even though I flushed it out and put new oil in. The exhaust muffler only had a cloth plug in it to keep dirt in the air out. Pic below is just off the web, when I get around to it I'll take a pic of the one I have here (identical to the advertising pic below).

alcatel2004aaa_chart.gif - 59kB

[Edited on 12-29-2010 by IrC]

watson.fawkes - 28-12-2010 at 14:40

Quote: Originally posted by IrC  
On the subject from another thread I must add my Plexiglas problems were insurmountable. I was buying it from various local hardware stores. Several attempts and every time I had problems with cracking with the slightest pressure, and epoxy failing to adhere. I am convinced this is due to the formulation and/or manufacturing of the Plexiglas now coming from China.
It's also possible that you're seeing the difference between cast acrylic and extruded acrylic. The cast product is superior and costs more. Guess which one is more likely in the hardware store, available to plastics newbies? I get my acrylic at a local sign shop, usually out of the scrap pile they sell off by the pound, since I rarely need anything window-sized.

While I saw your problem before, it didn't occur to me until today what the problem might be.

IrC - 28-12-2010 at 15:57

Thanks for the advise. Somehow I doubt if I asked they would even know the difference. No local sign shop just a couple hardware places. Made me sad to cut up my tank. I had saved it to build a big PCB etching setup, even had bought two pumps for circulation. Now I see I do not want to build one someday from anything available around here. Helpful info, when I do build another tank I will have to drive over 200 miles round trip. If they cannot say for sure it is extruded I will have to keep looking. Will have to study up on how to tell the difference. One thing is I noticed the old tank walls drill easily without trying to tear chunks unlike the local (cast?) stuff. When I was building with the new stuff I had to step up in 1/64 increments. Took only three bit sizes to get to a 1/4" hole with the old material, no sign of bit grabbing either. Cast you say. Good idea.

[Edited on 12-29-2010 by IrC]

vulture - 28-12-2010 at 16:12

You might want to invest in some fomblin or other perfluorinated oil, less oil mist and crap usually floats on top. Not really necessary if you don't use corrosive chemicals.

IrC - 2-1-2011 at 16:26

I don't pump down any chemical experiments, mostly physics type experiments. Looked at the price and it is high for that oil. For anything chemistry related I have a few Gast diaphragm types which would survive corrosion better and in general are inexpensive pumps. Thinking about removing the top pump as it barely does 150 microns and I need room for large tubing for the Alcatel. Besides I have learned through experience it is better for two pumps to be closer together in maximum vacuum capability.

Below are a few pics of my system. I built it for getting down in the 55 micron range and providing various plumbing to allow gasses in for laser work. Wanting to play with the Farnsworth Fusor idea I decided to find a way to include the Alcatel pump. That thing is 10 times less noisy than even my new two stage pump. Very smooth even if it could use a touch up paint job. I cannot measure the vacuum with it, will have to get some better gauges as it pegs everything I own. Looking at Pirani gauges and looking at plans to build a Capacitance Vacuum Gauge, still undecided.

Finished my top but am waiting for a freon leak checker (off ebay) as I cannot get below 100 microns due to a leak somewhere. I could not think of an easier way to look for tiny leaks. I still wonder if extruded Plexiglas is the reason. Next I want to build a cage around the bell jar just in case.

One last thing. Does anyone know where to get user info for Alcatel? Damn hard to find, with the name connected to Lucent in a completely unrelated technology. I am looking for oil level in the site glass information. What is full, over, under, etc., and off or running when you look in bubble in sight glass. Refilled it after flushing and is centered in the red circle on, raising to top of glass off. Looked natural that way, took exactly 1 Qt to reach this level. No idea for sure and with these things going for up to $700 on ebay broken - as is, I sure do not want to make any mistakes. Worth much more in perfect running condition as this one is. I never use my high quality pumps until I have already reached the 150 micron range just to keep them in top condition.

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[Edited on 1-3-2011 by IrC]

vulture - 3-1-2011 at 13:20


One last thing. Does anyone know where to get user info for Alcatel? Damn hard to find, with the name connected to Lucent in a completely unrelated technology.

I feel your pain, I spent quite some time digging up a manual for our alcatel vacuum pump on the net. It's on another computer and I'll try to find out where I got it tomorrow. Alcatels vacuum branch is now called adixen, but they don't seem to have manuals for older stuff on their website. They might be of assistance if you contact them, however.

IrC - 3-1-2011 at 14:56

Thanks Vulture. I searched that site a week ago but found nothing useful for the 2004A. In general all I found searching was rebuild kit parts lists and one part location PDF but not a word otherwise. By this I mean some form of rebuild instructions which may have included oil level info, etc.. Emailed but heard nothing back. If you ever find your file I would be happy to see it posted here. Just a little maintenance information would be helpful. Long ago I decided to not invest in anything the MFG makes hard to find info for but this Alcatel is so smooth and quiet (as well as very high vacuum) an exception must be made.

vulture - 5-1-2011 at 12:38

Attached you'll find a manual to the 2005 series of pumps, I don't know if it translates to your model. I got it from , maybe they want to help you out.

Attachment: alcatel 2005.pdf (988kB)
This file has been downloaded 659 times

[Edited on 5-1-2011 by vulture]

IrC - 5-1-2011 at 17:10

Thanks Vulture this PDF is perfect. Answered all of my questions. This plus the parts placement PDF for the 2004A give me all I need even if I never do find the correct owners manual. I will keep searching for a service manual if it exists just in case I ever decide it needs a rebuilt. With a flushing (wasting a QT of new high vac oil combined with refilling with a new QT (just under) it runs so perfectly I doubt I will ever need to rebuild it. I am amazed at the quality of Alcatel pumps.

IrC - 18-1-2011 at 17:36

Just an update and a question. I finally found my < 100 micron leak, it was the neoprene itself. 5/16" thick material and it is actually leaking through the material. I made a new seal with a new piece - same problem. I need to find some of the 1/4" stuff identical to the old one used in the big magazine lithography machines. No luck so far but I did learn it was a silicone type material which worked great under one micron.

Question: does anyone know of any sources for porosity information for various rubber-like materials? The neoprene I used was large 12"SQ sheets used for making automotive gaskets. Nothing else locally around here and as stated in another post those fleabay sellers want insane prices for their stuff.

For now I am working very hard to remove the old epoxy to reuse my original gasket. Not fun and I really want to make a brand new one if possible within my budget.

vulture - 19-1-2011 at 12:11


No luck so far but I did learn it was a silicone type material which worked great under one micron.

Be careful with which kind of silicone tubing you buy, IIRC some kinds of silicon polymers are actually O2 membranes.

IrC - 19-1-2011 at 14:45

Good to know if I ever decided to use flexible tubing. The material I was talking about is a big sheet to make the gasket for the base of the Bell Jar. Long ago I started using only Cu tubing and flare fittings for all vacuum lines. Once in a while I make connections with air conditioning lines (needle valves in ends) like are used on gauge sets. Not very often I prefer only copper but this can be hard depending upon what I am doing at the time. The Alcatel sure liked the cleaning and oil change. Seems slightly quieter, and I think even better vacuum but still waiting to get gauges. I also need to work on new plumbing say 2" diameter Cu to get better vacuum with the Alcatel. I have reached levels of evacuation I can no longer measure accurately with the stuff I presently own. Still looking at various gauges, looking to build my own ion tube. Have quartz tubing up to 2" diam. X 4' long but my oxy-acetylene outfit was stolen a few months ago and my budget has not allowed me to replace it yet. Was the only way I had to work with the tubing outside of my diamond wheels I use to cut it. Need the hot flame to seal electrodes, using pure cobalt wire for that. Want to build a plating setup to try plating Cu onto the wire where it goes through the glass or quartz depending upon what I am experimenting with. Probably the most difficult thing to do in a home setup is coming up with leads with the same expansion as the glass or quartz. Not sure that applied to your post, just thinking out loud.

peach - 19-1-2011 at 15:49

{edit}I only saw your reply mid typing this, so I realise you've already got some of it covered and that the neoprene is for the chamber seal. Neoprene is not a nice material at all. It's far too weak for hard chemical exposure, and it is porous yes. Whenever I think of it, I always get a mental image of a wetsuit. What are you thinking of doing in the chamber? You could start with natural rubber, silicone or polysulphide sealants. I'm not sure how they fair up in terms of numbers, but I suspect they'll all be better than neoprene. You could also try levelling the base of the bell jar and using a high vacuum grease instead. Some searching around can net you a desiccator that has a ground flange for use with grease. If you find the pressure isn't dropping how it should, my first port of call would be the copper fittings. If they're compressions, they are likely leaky and a soldered option may be the way to go.{/edit}

This is an old, but very nice to read, manual on vacuum, showing how the guys began working on it back in the day - rated A* by John


I have taken one of those Alcatel's to bits, screw by tiny easy to loose part.

If the pump has been barely run, I doubt it will desperately need a rebuild and you'd be best off checking what pressure it's reaching first.

As I have mentioned before, physics is far more demanding on vacuums. A prime component of the vacuum it creates is the oil in there, as it can end up full of solvent and water. Of coarse, if there is some 100C or below boiling thing in the oil, it will be trying to boil off and get out the exhaust as you run the pump; so the pressure won't drop to it's full extent until all of that is gone (vacuum pump oils were developed to have very low vapour pressures so they don't start off gassing under vacuum in the pump head). If you've just got the pump, and have a gauge handy, try connecting the gauge to it and leaving it running overnight to see if the vacuum increases over 12h or so. It will drop a little normally anyway as the pump head warms up, but if it keeps dropping all across the 12h period, there'll be something in the oil. It can take absolutely to get moisture out, so the gauge may just sit there and not move. Even lighter oils will create a problem, especially as they will likely have a higher specific heat capacity and so will take longer to boil off.

Mechanical dial gauges are okay for chemistry, but not much help for physics, because they can't pick up the changes very well as they approach the maximum of a rotary - the typical dial gauges can't pick it up at all actually, as most have at best 1mBar divisions, and the rotary can theoretically reach ^-3 mBar.

I was going to say, if it's been in the desert, that may be a good thing due to the heat and lack of humidity. But it depends where and how it was stored and what it was used for I expect.

Looking at the pump, I see signs of rust on the external components. That suggests it's been somewhere fairly damp, as I've not seen the rust on mine and 'grey drizzle' is the predominant weather system in the UK. :P

If you look at the photo I've included at the end, you can see the insides of these pumps (Alcatels) look a lot like a sandwich, with blocks that slide together. You can also see, they're CAKED in rust. This is quite normal in my experience, and is a sign that damp air has been running through it - e.g. people have been leaving the pump running in a workshop as they get something ready, or they've been using it to boil off moisture.

Opening a pump and finding it looks like this is not a great experience, but it's also less of a problem than it looks. The actual chambers inside are usually still shiny. The outside of the pump head rusts because the film of oil drips off it when not in use and the pump heads are often cast iron.

When you say neoprene seal, do you mean the one around the oil box (the orange thing)? That shouldn't actually be exposed to the vacuum, it's more like a collection pan that the oil sits in.

I would say you first goal should be a gauge so you can actually CHECK the pressure it's reaching, which is real important for physics work. If you're predominantly interested in lower pressures, there are a number of HVAC gauges you can buy that use the convection / thermal conduction properties of gas for measurement.

These are usually a lot cheaper than the pirani's in the link, but will read to 0.01mBar and can swap between units on the display. In my experience, they start reading at about 25 - 50mBar. Being able to swap between units so easily is helpful when every person you speak to seems to have their own preference for Pascals, PSI, microns, torr, mBar, ATM and so on.

If you search eBay for 'digital vacuum gauge', you'll see the HVAC ones come up at about $80 to $160.

You are right to save that pump for physics and use the diaphragms for chemistry. Provided they can get down to aspirator pressures, that's all that's needed for distillation, filtration and so on, and they are far easier to make chemically inert.

I believe quite a lot of semiconductor labs are now ditching their rotaries for alternative rough pumps (oil free) so they don't have to think about oil back streaming into the ultra high purity silicon as it's being processed - which is a problem for those guys as 5 minutes of reading about what they get up to demonstrates.... they need it to be clean, super, duper clean to an atomic scale. They've been using turbo pumps for quite a while over diffusions for the oil reason, but it's only been more recently that the vacuum companies have started coming up with suitable replacements for the rotaries that usually back them.

I have a turbomolecular pump (as soon as the guy gets back about paying for it), but the leap in complexity of parts and costs is gigantic from chemistry to that. For instance, normal seals aren't okay, and you have to start using bits of indium wire, copper gaskets, massive ISO flanges to avoid choking, the gas behaves in a none fluid manner, bake out ovens, metal hoses, at least two different (expensive) gauges. It's normal for an ultra high vacuum system to take a week or two of constant baking and pumping before it actually reaches the full vacuum; due to boil off inside the system and the time it takes for the remaining molecules to randomly bounce into the diffusion or turbo pump's intake.

Random is the word here, as they no longer behave like the gases we can suck out of a straw or with a rotary. Part of the reason for the bake out is to encourage things to boil off but also to increase the velocity of the molecules left in the chamber, so they are more likely to make a collision with the walls that will bounce them at an angle towards the high vacuum intake (because are making more collisions per unit time than they were at a lower temperature).

Due to the way the motion of the gas changes at this pressure, these pumps can't really be connected to the system by hoses, as it's effectively like trying to hit ping pong balls through a window tens of meters away - almost all of them will miss and bounce back. This is why diffusion and turbo pumps have such wide openings on the top and go on the bottom of the chamber. The length of the connection between the pump and the chamber is also important - it usually shouldn't be more than the flange is wide.

Being able to establish an ultra high vacuum has been one of the drawbacks of the new silicon technologies, like quantum structures. The huge amount of time involved in pumping the chamber down makes it slow and costly, and risks a lot if something goes wrong with a wafer in there.

Making your own ion gauge was something I was thinking about as well, but didn't put too much thought into it as I still have lots and lots of other bits that need collecting before it's going to reach ion gauge pressures. You can't switch on ion gauges and such until the pressure is right down. I think they tend to use iridium wire (a platinum, but with more mechanical strength to avoid warping of the electrodes / distortion / noise).

I would suggest you also ignore the ion gauge stuff until you have a system approaching a level that will need one - which means a diffusion or turbo pump and all the related components / seals. You need to be using metal components for that, plastics and rubbers off gas too much as you enter that region of pressure.

Calibrating a DIY ion gauge will also be an interesting challenge, as what do you have to calibrate it against? :P

I was thinking my first bit of high vacuum physics would likely be PVD, and sputtering some mirrors - for a laser / telescope.

If the pump has been used to move cylinder gas, it's could just be rusty on the outside. Even if there is rust on the pump head, provided the actual chambers are clean and free of sand, it'll still be okay.

Any thoughts, I'd be interested to chat,

When moisture strikes.

[Edited on 20-1-2011 by peach]

IrC - 20-1-2011 at 00:27

If you look at the pics above you will see the Bell Jar sits on a flat Plexiglas surface. The gasket in question is just a simple ring about 7" diameter, 1" wide, epoxied to the surface. The Jar sits on that. Before I had to rebuild the top I had one I cut from a sheet that had near zero out gassing, the neoprene nightmare blows. Or is it sucks? The pump has little use on it. But it was stupidly stored on the floor in a closet with jugs of every acid and combination of the nastiest assortment of chemicals. Some of the metal cans were paper thin and rusted beyond belief. Some had bottoms falling out. A real pain safely and properly cleaning up the closet and getting rid of the trash.

When I stored the pump in my desert location it thanked me for getting it out of hell. Inlet and outlet were well sealed all this time and the pump internally is as spotless as can be. Only used for intermittent experimenting, all the old look you see on it was simply from fumes around it as it sat in on the floor. The oil was clean and clear, I just changed it because I am picky and I did not like where my little brother had kept the pump. Everyone keeps mentioning about what goes on when the pump is moving much gas or air but I can tell you it never saw this.

Myself, I never turn a good pump on until the vacuum is at least down to 200 microns quite simply because I spent too many years of life never owning a really good one. My brother got married shortly after he bought this one, she was always on his ass about wires and chems and things so he rarely ever did any neat experiments. Probably part of why he is on second wife now and she is cool, into science and things but too bad, so sad, the pump has been mine for years and he can't have it back. Actually he has another new one now anyway.

At least I taught him about what to store around what, where, and why. I had stored it for several years fighting illness, never getting to do much of madsci. Not out of it completely but better enough to go crazy with some things that look cool. Actually, I am playing with my vacuum setup now as i want to play with putting layers on quartz to make optical filters. Mostly because I want to build a UV camera and for the money everyone wants for bandpass filters to hell with that I am going to build mine if at all possible.

When I am doing something with vacuum I have more than 10 different pumps and always use the crappy ones to move a large volume of anything. Only when there is little air or other gasses left to move do I run my two good ones. By the way thanks for that great link I am reading it now. Good stuff.

[Edited on 1-20-2011 by IrC]

Tiberius_C - 20-1-2011 at 00:49

Just a short note -- if anyone is still looking for cast vs extruded acrylic, McMaster-Carr carries it. Their website is

Prices aren't the cheapest overall, but I can vouch for their excellent customer service & prompt delivery.

IrC - 23-2-2011 at 18:29

This person is really good at working with glass for vacuum applications. I thought some of you might find his information useful.

Regolith - 24-2-2011 at 11:27

IrC Thats outstanding. I spidered his whole site and added it to my glassblowing archives.

That's pretty much an excellent starting point for both making vacuum devices like triodes etc and glassblowing in general. He uses basic torches and things average people have just laying around. Although I have issue with some of his technique, breaking glass towards him, anyone who can make there own filament light bulb gets a pass for the minor things. The zombies show up and your even making your own light bulbs... your set.

peach - 24-2-2011 at 12:26

'Filament' is a dirty word! And soon the police will be raiding houses to find guys naked and surrounded by 100W filaments and wads of cash at 3am. As they have now been taken out of production, yet are so good for using on dimmers.

Prepare to jizz in your pants gentlemen. Get a cup of coffee first and then enjoy;

<iframe sandbox title="YouTube video player" width="480" height="390" src="" frameborder="0" allowfullscreen></iframe>

<iframe sandbox title="YouTube video player" width="480" height="390" src="" frameborder="0" allowfullscreen></iframe>

I would like to visit this man's house. And then never leave.

Magpie - 24-2-2011 at 13:39

It is indeed a pleasure to watch a skilled craftsman make an intricate and antiquarian device using specialized equipment. I wonder if he makes a profit making those tubes. Maybe he doesn't care.

peach - 24-2-2011 at 15:19

I'm not sure, but I know tube fanatics will pay serious money for some of that stuff.

A top end hi-fi from these guys is going to set you back a good chunk of a million quids, or more. A lot of it is full of silver, since it's ever so slightly better at conducting*** or uses cobalt / mumetal for the magnetics

Prices? If you have to ask, you're too poor. Get on with listening to your filthy 'dubstep' and 'rock and roll'.

I love the guy in the videos. It's what I'd like to be doing at his age. He's not just messing around painting kits, he's got all his stuff together and is doing something really well. Something I haven't seen other people doing.

***During the development of the first nuclear weapons, the US government had everyone hand over their silverware to build the coils for the separator. :D

[Edited on 24-2-2011 by peach]

Regolith - 24-2-2011 at 17:49

Yes that was amazing as hell... Also yes tubes these days are stupid expensive. Russia only recently started again making tubes. They had stopped after the fall much to the dismay of audiophiles. People were recycling used tubes from old radar equipment for audio systems for a while.

Oh and rock and roll sounds amazing through tubes. So does dubstep I might add :). Tubes generate harmonics not heard in transistors, or rather in a transistor it distorts with random interference. In a tube the distortion is harmonic to the sounds going through it.

This seriously makes me want to make my own tubes as well. I buy them when I get a commission for a new amp. Peach is as usual correct. This slab of black walnut and the tubes shown will be combined with transformers (pure silver wire wound toroids, that's getting to be the price of the tubes themselves) to produce a tabletop tube amp. Price tag, over 1000 dollars for a simple design.

02242011295.jpg - 104kB

IrC - 24-2-2011 at 18:24

I would not use beam pentodes for quality sound. Save the 811's for a freaky Tesla coil. Build your own sockets and use a pair of 813's. Besides in the winter you could shut the heat off and bask in the warmth of monster glass jugs which are far more linear with greatly reduced odd harmonics. Being rated to 20 MHZ or so you will have no problems mixing the ultrasonic products which add depth and presence in the audio range. I used two 813's from an ion implanting machine from Microchip in Chandler to build the most powerful tube type Tesla coil I ever created. Last time I saw it was in the instrument Lab of Arizona's power company Salt River Project. Never loan cool toys to friends I say. He likes it so much I cannot get it back.

Of course now you have ruined it, I should have been thinking stereo. If only I had known. The pain of it all. I am stuck listening to MP3's on this computer.

Just realized I forgot to add:

When light bulbs are outlawed only outlaws will have light.

[Edited on 2-25-2011 by IrC]

Regolith - 24-2-2011 at 18:56

Oh it's not for me :D, 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 :)

IrC - 24-2-2011 at 20:39

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.

Regolith - 24-2-2011 at 21:09

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 :D

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.

IrC - 24-2-2011 at 21:40

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.

1155.jpg - 58kB 1162.jpg - 38kB

[Edited on 2-25-2011 by IrC]

starman - 4-3-2011 at 22:39

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.

Lord Emrone - 6-3-2011 at 07:41

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 ?

this with a spherical-shaped flask and tube is all I need then ?

watson.fawkes - 6-3-2011 at 10:06

Quote: Originally posted by starman  
Do you think its worth the money for the one with the pirani sensor(inficon about $190)?
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.

peach - 6-3-2011 at 10:38


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]

Contrabasso - 6-3-2011 at 10:50

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.

Lord Emrone - 10-3-2011 at 10:02

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 ?

this with a spherical-shaped flask and tube is all I need then ?

can someone please answer my questions ? ;-)

Picric-A - 10-3-2011 at 12:28

Quote: Originally posted by Lord Emrone  
... but I'm not really into chemistry ...

If your not really into chemistry what are you using the Ammonium Nitrate for?

starman - 11-3-2011 at 10:08

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]

Lord Emrone - 12-3-2011 at 09:11

Quote: Originally posted by Picric-A  
Quote: Originally posted by Lord Emrone  
... but I'm not really into chemistry ...

If your not really into chemistry what are you using the Ammonium Nitrate for?

Energetic Materials.

Arthur Dent - 12-3-2011 at 13:05

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! :D

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!


How to best use RZ2.5 Rotary

trb456 - 12-3-2011 at 18:20

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,

watson.fawkes - 13-3-2011 at 07:33

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.

trb456 - 13-3-2011 at 09:34

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.

chemrox - 24-4-2011 at 11:00

I hate anything that requires flash. Adobe doesn't bother to keep up. Mac-like arrogance.