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S.C. Wack
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Excellent use of cheap glassware!
You would think this would be illustrated in the student lab manuals, but no, just the kind I indicated earlier...but then, they rarely mention
insulation.
Quote: Originally posted by blogfast25  | | I'm also interested in SC's alternative that he wrote about a couple of posts ago but haven't really found anything. What he called a 'thermometer
bulb'... |
A more pure and true blogfast25 response could not have been composed, in response to the sentiment that distillation/column heads have traditionally
been known as distillation/column heads and not as "reflux splitters", (at least outside of the arcane world of chemical engineering) until
(apparently) recently.
With organic kit glass yes imperfect insulation could be desirable, but at least for the usual higher boiling distillates you're still going to need
insulation. It would be wiser to have thin insulation all over instead of insulation only over part of the fractionating area.
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Magpie
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| Quote: Originally posted by blogfast25 |
In the case of your Hennion gadget, clearly you can set reflux with it but do you actually know the value of the reflux ratio? Methinks not but please
correct me.
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You have to determine the reflux ratio by counting drops, both at the drip tip of the cold-finger, and at the receiver.
| Quote: Originally posted by blogfast25 |
Clearly if that bottom valve is closed you run at total reflux but if that bottom valve is fully open, does all condensate flow in to the distillate
receiver? It's not clear from the photo.
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Yes. The drip-tip is directly above the opening of the tube going to the receiver.
| Quote: Originally posted by blogfast25 |
As pointed out a much simpler geometry uses a timed valve. An overhead condenser on top of the column condenses all of V, then directs the condensate
for 'x' seconds back into the top of the column and for 'y' seconds in to the distillate receiver. I've seen this used on a pilot plant rectifying
column for high grade methanol I used to work on some 30 years ago, as a student.
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Apparently that device works OK then? When I first read about it it didn't sound good. I thought that the constant flow interruptions would cause
disturbances to the column equilibrium.
| Quote: Originally posted by blogfast25 |
I'm also interested in SC's alternative that he wrote about a couple of posts ago but haven't really found anything. What he called a 'thermometer
bulb'...
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I assumed that this was SC's tongue-in-cheek description of a de facto condenser formed from the uninsulated column head/thermometer
adapter/thermometer. 
The single most important condition for a successful synthesis is good mixing - Nicodem
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Little_Ghost_again
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I often bodge glass ware to make an approximation of something I have seen in the books.
Mapgpie can you do a couple of clear pics of your please? I have an idea how I might be able to do that on the cheap  .
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Little_Ghost_again
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baffcat has them alot cheaper than £99 and no I am not telling until I can afford one lol.
Oh ok look up peking triangle in his shop, thats pretty close to what you want
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Little_Ghost_again
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I thought I might as well try and add something of use. I now have a real cold finger (no jokes please) but my first I made, I found a small thin test
tube with a reasonable thick bottom, heated a solid glass tube and the bottom of the test tube together (like in the books) and pulled a bit, I wasnt
after a cold finger but something else I had read in vogel, however the bottom of the test tube became pointed and the glass rod detached.
I was about to try again when I thought..............Hang on that looks alot like a cold finger, so I stuffed and sealed a two hole rubber bung in the
top and used a pipette to draw a couple of tubes slightly thinner near the bottom. I then put one in the tube near the bottom and one near the top,
the whole thing was then covered in araldite glue (no idea why it just seemed like a good idea).
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blogfast25
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| Quote: Originally posted by Magpie |
Apparently that device works OK then? When I first read about it it didn't sound good. I thought that the constant flow interruptions would cause
disturbances to the column equilibrium.
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Yes, it works well. I saw it used on a larger size column (about 20 cm diameter) but even on smaller columns those disturbances don't affect overall
outcome much.
@LGA:
I think you mean 'Perkin (not Peking) triangle':
http://www.ebay.co.uk/itm/RA6-33-Intermediate-Perkin-Triangl...
But that's not a distillate splitter.
[Edited on 19-10-2014 by blogfast25]
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Magpie
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Here you go Little Ghost:
The single most important condition for a successful synthesis is good mixing - Nicodem
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Little_Ghost_again
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LMAO yeah thats what I meant! and correct after looking at it I realized I was talking shit sorry.
Magpie thanks alot, I am thinking that isnt too hard to approximate cheaply .
time to see how good my glass melting has got
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DJF90
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@Magpie: Fractionating heads can get rather elaborate, and I've,seen some with "swinging bucketsv before. A bucket and chute is attached to the bottom
of the reflux condenser, in a way that allows it to,swing back and forth. A magnetic strip is embedded in the chute, which normally sits above the
column (liquid return). An electromagnetic controller is placed inline on the outside of the glassware, an operates on a x seconds on, x seconds off
sequence (like PWM I guess...). When the electromagnet is on, the bucket swings across to position 2, where the chute sits over the distillate
receiver. Its a very automated and accurate way of setting reflux ratio, but also an even more expensive setup. Normag make fraction dividing heads
like this.
And especially for you, blogfast...111215225328
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blogfast25
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Nice number but what does it mean?
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Little_Ghost_again
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probably a ebay number
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Dr.Arz
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Is it efficient to pack multiple glass fraction columns top by top, like two or even three 400mm? Can distilling speed be increased with keeping up
the purity by increasing column height? How suitable stainless steels of 300 and 400 series are for packing columns?
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blogfast25
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Yes!
http://www.ebay.co.uk/itm/111215225328?ru=http%3A%2F%2Fwww.e...
£97.50 and it still needs a condenser on top of the larger female ground glass joint. In fact it' not entirely clear to me how this thing's supposed
to work.
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blogfast25
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| Quote: Originally posted by Dr.Arz | | Is it efficient to pack multiple glass fraction columns top by top, like two or even three 400mm? Can distilling speed be increased with keeping up
the purity by increasing column height? How suitable stainless steels of 300 and 400 series are for packing columns? |
All other things being equal, longer columns have higher separation power. And as a consequence separation power can be sacrificed for speed with
taller columns. But you need to be realistic with column diameter too: how much vapour can you send through an inch of pipe diameter without pressure
build up, for instance?
Stainless steel? That will depend entirely on the stuff you're distilling. AFAIK everyone uses glass or ceramic packings.
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S.C. Wack
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Naturally, I use SS. It may not be for the best, IIRC different materials in the same form do not separate the same.
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Little_Ghost_again
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Personally for that money I would stick to claisian adapter cold finger and the bit where the valveis I would just use a rubber bung with a glass
stopcock going to another bung at the condenser if that makes sense, far far cheaper and exact same job. Only real difference is the swivel joint but
I am not a fan of them
[Edited on 20-10-2014 by Little_Ghost_again]
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Little_Ghost_again
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I must spend way too long looking at porn on ebay! I need to get out more now I can recognize ebay numbers lol. If you want one message baffcat on
ebay he is open to offers normally
Or use my method and pay me £5 license fee lol 
[Edited on 20-10-2014 by Little_Ghost_again]
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Fulmen
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Question; What is better for a given column: A perfectly insulated column and top condenser or a perfectly tuned cooled condenser?
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Magpie
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I use broken glass packing or a stainless steel scrub pad. For the broken glass just take a thin-walled food jar and smash it to the appropriate size
for your column. BTW, the ss scrub pad was first suggested by Louis Fieser I believe, as a cheap but effective column packing.
My experience is that the ss scrub pad is somewhat more efficient than the broken glass. But glass is more chemically resistant. I found out that
the ss scrub pad cannot be used when distilling acetic acid due to severe corrosion.
If cost was not an object I would pack my column with this:
http://www.sigmaaldrich.com/catalog/product/aldrich/z210536?...
[Edited on 21-10-2014 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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DJF90
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| Quote: Originally posted by blogfast25 |
£97.50 and it still needs a condenser on top of the larger female ground glass joint. In fact it' not entirely clear to me how this thing's supposed
to work. |
Just like any other stillhead, it needs to be used with a condenser and thermometer. Receiving flask attaches to the joint the other side of the
stopcock. Really not rocket science...
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Little_Ghost_again
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I use 2mm glass beads sold on ebay with a hole in the middle for packing, 20 different colours available apparently, I tried broken glass but couldnt
afford the plasters, if I am lazy I use SS scrub pad thing, again watch the thicker one it slices your fingers open and sting worse than a paper cut.
I advise on plaster as some compounds make you hop about a bit if they get in a cut.
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Fulmen
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Choice of packing is usually a compromise between surface area and holdup, the perfect material should have a huge surface area but little volume to
reduce holdup and risk of flooding. Raschig rings seems to be a good place to start.
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blogfast25
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| Quote: Originally posted by S.C. Wack | | Naturally, I use SS. It may not be for the best, IIRC different materials in the same form do not separate the same. |
Like Magpie I've used an SS scouring pad. Worked well but I'm not comfortable with any acidity in whatever you're distilling.
| Quote: Originally posted by DJF90 | | Just like any other stillhead, it needs to be used with a condenser and thermometer. Receiving flask attaches to the joint the other side of the
stopcock. Really not rocket science... |
I was looking at it wrongly: it looked to me as if the thermometer tube was passing behind the condenser tube but it's not.
A slight improvement would be to lower the connection between the bend in the condenser tube and the distillate tube. Also: needle value instead of
T-valve, the latter are harder to adjust flow with.
[Edited on 21-10-2014 by blogfast25]
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DJF90
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Glad you can make sense of it now. I personally think your suggested improvements are redundant: the distillate take-off tube is adequately positioned
and I find the stopcock fine, although thats personal preference. The bore however is large enough to enable fairly fine adjustment, and groves can be
made with a diamond file to improve control if required. The newer part by Quickfit does use a rotaflow valve, however I tend to avoid these where
possible.
More beneficial would be shortening of the distillate take-off (reduce dead volume), possibly by removal of the ball joint (although this is useful
for taking up some of the strain). The significnt disadvantage of this setup is the inability to operate at reduced pressure without bodging together
several other components (a couple of 3 way taps, a straight vacuum receiver adaptor and a hose barb for atop the condenser), which will likely be a
major ball ache. However for recycling solvents it would be more than adequate.
Considering the materials cost for the glass joints and stopcock, I'd say 100 quid is a fair price. But if you can get one like Magpie has for a
similar price, or reduced pressure work is a necessity, then get that instead.
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Little_Ghost_again
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these rachel rings? they are little more than glass tube bits cut 2-3mm long arnt they?
I got a box of broken pipettes I could cut up thats got to be pretty close?
[Edited on 21-10-2014 by Little_Ghost_again]
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