Sulaiman
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What is the bulb in a drying tube for ?
Here is a typical drying tube
What is the purpose of the bulb ?
(YouTubers typically stuff it with cotton wool etc. which does not benefit from a bulb as the other end is plugged with cotton wool also, so the tube
may as well be straight ? )
CAUTION : Hobby Chemist, not Professional or even Amateur
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NEMO-Chemistry
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Its for the plug of wool
Actually i thinks its so the plug of wool dosnt mess with air flow, air dries but travels through desiccant slowly, reaches the bulb with wool in and
then enters more narrow bit, by have a bigger bulb you make up for the lower volume speed.
If you see what I mean.
[Edited on 29-1-2018 by NEMO-Chemistry]
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JJay
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I have always plugged the small hole below the bulb with a small piece of cotton and filled the bulb with desiccant. *shrug*
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Sulaiman
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That makes sense, a small plug of cotton wool, as when searching for the answer (before asking here 
one reference referd to it is an increased reservoir capacity
Thanks
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NEMO-Chemistry
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Quote: Originally posted by Sulaiman  | That makes sense, a small plug of cotton wool, as when searching for the answer (before asking here
one reference referd to it is an increased reservoir capacity
Thanks |
I am only quoting an answer I was given at school, i also wanted to know  . If
you plug below the bulb then the plug can go in the reaction (unlikely buy hey), desiccant passes air more slowly than an empty tube, so the bulb hold
the cotton plug and also gives a lager area of dry air.
I was told that is also why the bottom bit is smaller, so the plug cant get sucked in....
I use it the way I describe, but only because thats what I was told. for all I know it might just be to make them more sexy .
Funny enough I got loads without them as well.
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zed
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Well, the drying tubes I used to use, usually hung upside down, from a piece of latex tubing, affixed to the top of a condenser or whatnot. The
bulb was packed with desicant, the open end of the tube was stuffed with glass wool.
In fact, upside down is still probably best. That way, your desicant doesn't liquify, and drip into your reaction product.
https://www.ebay.com/itm/75-Bent-drying-glass-tube-adapter-2...
https://www.ebay.com/itm/U-Shape-drying-glass-tube-adapter-2...
I need to hear a song. https://www.youtube.com/watch?v=LtaLI74XFtU
[Edited on 31-1-2018 by zed]
[Edited on 31-1-2018 by zed]
[Edited on 31-1-2018 by zed]
[Edited on 31-1-2018 by zed]
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Sulaiman
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THANKS !
That seems to be the most logical
... open end down and plugged, with the bulb full of dessicant.
The secret is in the third link above ...
CAUTION : Hobby Chemist, not Professional or even Amateur
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j_sum1
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I don't have much experience with these. I have two: a straight one and a 75°. (I don't have a u shaped drying tube.) Both have seen little use.
It does seem to me that there are two main ways they are used. One for drying a gas coming from a flask. In this case you have a bung and hose. The
other is for preventing atmospheric moisture from entering the flask. I would not be prepared to bet the same orientation and packing was best in both
circumstances.
My inclination is to fill the bulb with loose-packed wool and the tube with dessicant. I reasoned that this would allow the gas to spread over a wider
radius before passing through the drying agent.
I have occasionally wondered, in this age of ground glass joints, why rubber stoppers are used. It would seem better to have a female joint at the
other end.
But then, what do I know?
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zed
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Ummmm. The stuff most of you guys are using, we used to call Microware. Small sizes, expensive, very convenient, compact. Ground glass joints on
all of the pieces. Transport a mini-lab in a suitcase.
Used to be, stuff could be larger, and fit was not a problem, because you could use rubber or cork stoppers, and a hole borer, to fit virtually any
kind of arcane apparatus together.
Utilizing a thick walled, 5-10 gallon Pyrex bottle, was not unheard of. In fact, you could buy one for about 50 bucks new. Nice to have one around.
Or, maybe even a couple.
Drying tubes were not expensive or "special glass". They were cheap as dirt. Probably less that a buck apiece. Much less. And, ordinary
unjointed glassware, was strong, inexpensive and plentifully available. It was Vogel-esk.
Tubes looked like this https://www.indiamart.com/proddetail/drying-tube-15983420862...
Fill the tube with desicant, plug the open end with glass wool or cotton, hang it from a latex tube, connected to your apparatus.
Whoops, just checked. Perhaps I'm not as retro as I thought I was. Cork borers are in good supply on e-bay. Sharp as bejesus, by the way. You may
feel the urge to touch, or test the sharpness, of the sharpened tube end. It is Razor sharp, in fact.
And it will cut your fingertip badly, with zero pressure applied.
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p23800...
Lowes by the way, seems to sell rubber stoppers. They call 'em Hillman, black neoprene, hole plugs. Nice huh.
[Edited on 31-1-2018 by zed]
[Edited on 1-2-2018 by zed]
[Edited on 1-2-2018 by zed]
[Edited on 1-2-2018 by zed]
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