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Thermal
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[*] posted on 7-3-2005 at 19:03


Taz - I would imagine they would be as I'm pretty sure they're meant for using with a rotary evaporator.
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Quince
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[*] posted on 8-3-2005 at 21:55


Regarding hoses, how can I connect the hose to my water tap? I still want to be able to use the tap; are there any switched splitters that will allow the type of rubber hose to be connected? Also, would there be any problem if I ran the water through the condenser and aspirator in series, to save water? Due to the fast flow the aspirator needs, I don't think the water would heat much going through the condenser, and thus vapor pressure and aspirator performance should be little affected.



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[*] posted on 8-3-2005 at 22:24


Quince:

I use a kitchen sink tap with internal (female) threads. I bought a chrome plated brass aereator with the same thread size (only male), gutted it, and soldered my brass aspirator to it.

I did the same thing for cooling water suppy only soldered a brass hose barb to the outlet.

My aspirator takes a lot of water at a high pressure. My condenser takes very little water, at a low pressure. I have yet to need to use them both at once. I suppose for vacuum distillation you would. In that case I probably would put a tee upstream of the aspirator. The line to the condenser would then require a valve to reduce pressure.

[Edited on 9-3-2005 by Magpie]




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Quince
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[*] posted on 9-3-2005 at 23:51


Well, I have an all-glass aspirator, so I can't solder/weld.

I don't know what else I could possibly use vacuum for other than distillation (and I guess to speed up drying).

I came up with a solution using various sizes of aquarium air tubing. Since they didn't have splitters that were large enough to provide a good flow rate, I simply cut holes in the tube sides and used that neat polyurethane glue that foams and expands as it cures to connect the other tube, making a splitter/combiner. I'll get some valves from the HW store to switch on/off different combinations. I'm going to get a bucket and a water pump that can do 30+ psi so I don't have to waste all that water with the aspirator, recylcing it instead; that has the additional advantage of providing a smoother flow rate.

[Edited on 10-3-2005 by Quince]




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neutrino
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[*] posted on 10-3-2005 at 03:21


Quote:
Originally posted by Quince
I don't know what else I could possibly use vacuum for other than distillation (and I guess to speed up drying).


Vacuum filtration?
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[*] posted on 10-3-2005 at 04:27


In pictures on Google's Image search when I type in vacuum filtration, I see the buchner funnel is put on a flat-bottomed flask with a vacuum connector. I thought flat bottoms were not supposed to be used for vacuum. What if the filter or funnel gets clogged; might not the flask break then as internal pressure falls? I have one of these but haven't tried it yet because of that worry.

[Edited on 10-3-2005 by Quince]




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Blind Angel
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[*] posted on 10-3-2005 at 04:32


Usually those filtration erlenmeyer have thicker wall that the normal.



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[*] posted on 10-3-2005 at 06:06


I guess they are also not being heated while used for filtering, though I don't know if that actually makes a difference.



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[*] posted on 22-3-2005 at 12:09
Column packing


Currently, I'm going with small chunks (5-7mm a side) of broken pyrex. I took the hoarded pieces of a broken pyrex bowl, chipped them up with a hammer, then subjected them to a good shaking to round off the sharp edges.

So, a question for those of you with plain fractionating columns: what do you use for packing?
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[*] posted on 22-3-2005 at 13:44


You can get the Erlenmeyer flasks in plastic if you're worried about them breaking under vacuum.

I once made my own 5L Erlenmeyer flask using the method described in Nimble's book. (I hear there's a scanned version going around - not that I've seen it). Drill a hole near the top of a demijohn and glue a teat (see your plumbing supply section) on/in. You can stick a tube on the teat. Drilling a hole in one of those demijohn's is tedious indeed but it did work. You need a spade type drill for use with tiles. A 5L Erlenmeyer is scary to use; best cover it in plastic wrap or mesh should the unthinkable happen.

One tip is to visit your local flea market and get one of those Pyrex rolling pins from days gone by - makes a great fractional distillation column when packed with broken glass. Nice and thick too for vacuum fractionation. But doesn't fit in too well with jointed glassware. You will need to use rubber stoppers top and bottom with appropriate adaptors.

Demijohn and rubber stoppers used above - ex-wine-making supplies from the local garage sale or flea market.

Column packing - I just got loads of old flourescent light fittings and broke them carefully at either end. The white powder is easily cleaned out by shaking followed by washing. Stick them in a platic bag and gently hammer them. Use two sieves (garden centre) to get the appropriate sized glass.

Last tip is to shell out for a thermometer pocket for those vacuum distillations. I broke a flask once when the vacuum came on and sucked the thermometer into the apparatus making a neat hole in the bottom of my flask with a right mess all over my mantle as the oil leaked out. Thermometer pocket? - now you know why I want one. Don't let that happen to you.

The other trick for a vacuum pump is to get the pump from an old fridge and put that to work. Those pumps don't draw a lot of air but they do give an efficient vacuum. If you need a better vacuum from cheap pumps you can put two pumps in series.

[Edited on 22-3-2005 by CherrieBaby]
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[*] posted on 22-3-2005 at 15:06


For my small fractionating column (22/29 gg fittings) I have found that a stainless steel scrubber pad, not packed in too tight, works very well for liquids that are compatible with this undefined type of ss. Acetic acid is not compatible with this ss and it was promptly dissolved. :D For acetic acid I'm going to try some glass beads. I'm also thinking of cutting up some 5mm glass tubing to make Raschig rings.



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Dave Angel
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thumbup.gif posted on 22-3-2005 at 17:31


Cherrie:
Your tip about the thermometer pocket may one day save the life of one of my precious few flasks, avoiding one of those altogether unpleasant "ARGGH!" moments and a post in 'tragic glassware'! Nice one, though I'm sorry you had to learn the hard way...

Magpie:
I also considered homemade Raschig's, as those I've seen for sale go for £100+ for a litre pack, so that option seems a little uneconomical. I haven't yet managed to find myself a nice, cheap glass tubing cutter though, so it's not happening right now.

I used broken pyrex for my chunks as I thought that was best considering heating being involved, but perhaps for such small pieces of glass it wouldn't matter? If so, then standard glass beads have proven much easier to track down than pyrex ones, as I guess there's not much call for thermal shock resistant jewelry! :D
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[*] posted on 22-3-2005 at 18:46


I wouldn’t go with cheap glass, as it’s usually comprised of a lot of oxides (like sodium and calcium, thus soda-lime glass). What I think we have here is a use for Bomex. Think about it: unreactive borosilicate (or so they say) glass, very easy to break :D, cheap…
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[*] posted on 22-3-2005 at 19:15


I bought a glass tubing cutter for $11 through Carolina Biological. It works quite well - a quick score, snap and you have a clean cut.

CB supplies teachers so works to keep the prices down. Also you can usually buy even small items individually. You might have an equivalent supply house in the UK.

I know borosilicate glass is much more resistant to thermal shock than soda-lime glass. But I don't know which is more resistant (in general) to chemical attack.




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[*] posted on 22-3-2005 at 22:51


There are small supply houses in the UK but home experimenters are scrutinised more here. The relationship between the cops and suppliers is much more pally and involves the cops ensuring that suppliers "self-regulate" = squealing on any suspicious looking people.

A few years back I turned up at my supplier and was surprised to see a guy I'd never seen there before who I was told was "helping out". As I negotiated my order and packed my gear, he proceeded to ask me questions, from time to time, in a nice way, about what I was doing with this gear. All very innocent looking but I wasn't fooled. I was a bit dissapointed by this because I'm not very suspicious-looking at all. But in all honesty, some of the things I got were at odds with my stated application.

Cheap borosilicate is easy to pick up from flea markets. Old coffee pots do the trick, these make nice flasks (with handles even!), so one is resistant to smashing them up for the column packing.

Cheap glassware - I've never had a piece of glassware fail on me. So long as it's borosilicate and has no obvious flaws I regard it as OK. Tip for buying 2nd-hand glassware - look for flaws such as tiny bubbles - those flaws will be the site where the glassware first fails. Although you can get away with using such glassware it is pretty risky. Better scrap it and get something without flaws; that can be part of the pain of using eBay.
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[*] posted on 19-5-2005 at 06:26


The tip for buying 2nd-hand glassware ;)and collections by browsing the web are good.
Reminders of insolvent firms, high scools
and privat inserats.
Cheap borosilcat glass are also good for condensers.
Only much heat sensitive.
Comparing the price is important.
It existing some cheap offers of small firms
and markets. for glassware collections.

[Edited on 19-5-2005 by Madandcrazy]
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[*] posted on 20-5-2005 at 03:21
Glass


Dave Angel, I use small glass beads in the reflux column of my still(Ah ! Moonshine ! :D)
I found them at an arts and crafts store. May not be suitable for refluxing some substances
but works great for booze ! May or may not work for you but cheaper than Raschig rings.

Quince, I have filtration flasks ranging in size from 250 ml to 5 L. I use 1 of those manual vacuum
pumps found in most auto parts stores. For distillation I use a glass apirator. For air-conditioning
applications I use a rotary vane vacuum pump.




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[*] posted on 20-5-2005 at 04:29


I was thinking about going with a UGT distilling kit...

What I did instead was look around at all the parts I would want on ebay and total up the cost.. It came out cheaper to buy them seperate (no surprise) so I ended up buying my enitre kit each piece diffrently...

Heres what it looked like:
1000ml RBF from UGT
500ml RBF from Kantu Scientific
400mm Liebig from Kantu Scientific
Thermometer from Kantu Scientific
Thermometer Adapter from Kantu Scientific
3 way from 2 dog treasures
Other kind of 3 way danrfink
Hose inlet adaper from Kantu Scientific

Total price was under $150 (this includes shipping).. Of course now I have spent more than $350 getting stuff... some misc. items I have gotten are a 50ml jacketed raction beaker (for $20 I couldnt pass it up), a 15kv transformer, some beakers and graduated cylinders, a triple beam balance, and some other stuff...

Moral of the story is to shop around :)

I even bought some chemicals (propylene glycol, sulfuric acid drain cleaner, glycerin, etc..) Now... If only I could find toluene for somewhere for less than $11 per 500ml...




Duster
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[*] posted on 20-5-2005 at 05:55


Duster,

150 $ is a small pice for the kit.
Whats the acronym UGT kit ?

I think so, it is correct shopping arround to buy chaep.
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[*] posted on 20-5-2005 at 10:42


Doesn't Kantu sell mainly Bomex?
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[*] posted on 20-5-2005 at 20:59


$150 isnt too bad, a lot of the saving was from combined shipping and what not...

UGT (United Glass Tech) seels more expensive glassware but it IS better, better being thicker and all around just better. However I didnt have that kind of money to spend. I figure as time passes I will buy some more UGT and other high quality glassware as it comes. Right now I just wanted something to distill nitric with... And I think I got that.

As for the Bomex, I cant anwser that... I personally dont know, but we'll see here shortly... Whats so bad about Bomex anyway? Im curious...




Duster
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[*] posted on 21-5-2005 at 05:14


I've had some bad experiences with this Chineese glass. For example, I had a 2L beaker at around 90*C. I added water (to wash it) and the entire bottom fell out. Pyrex would never do that.
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