Author Topic: 500ml 3-neck flask uses?  (Read 45737 times)

0 Members and 1 Guest are viewing this topic.


  • Guest
500ml 3-neck flask uses?
« on: September 05, 2004, 08:18:00 AM »
What exact role does the 500ml 3-neck flask play in  reactions of importance either illicit or legitimate.

I just had to get this 3-neck flask, just because I payed $1.59 + 6.99 shipping for it and it is a cute little piece of craftmanship. But aside from a friggin' waterbong, what are these 3-neckers used for extensively. Cuzz thats all I'm using it for right now. But not why I bought it. 19/22 is exactly the size of the $1.00 1000ml volumeric flask I also got ebay style.  So help a mofuggy out?
I know that a stirbar and magnetic stirrer are usually used with them, but why are they used and in what way that makes LE officials look at them like they've got some clandestine connection and thats all they would ever think when seeing a 3-neck flask while on duty or in a search.

It hit killer as fuck for a water bong, but I want to use it for making some kind of ghetto gumbo. Ya'dig?


  • Guest
« Reply #1 on: September 05, 2004, 08:30:00 AM »
similar multi neck flasks are usually used for small reactions requiring multiple probes eg temp/pH

In a clandestine setting, you could use the centre neck for a reflux column, the side arm fitted with a stopper/thermometer, and the other arm could be stoppered and used to add reagents.  Then use for distillation of the end product.

Seems like a nice LWR setup...


  • Guest
For example
« Reply #2 on: September 05, 2004, 08:45:00 AM »
In one neck you put a condenser, in one neck you put an addition funnel and in the middle neck you put a mechanical stirrer. Why? Well, some reactions need such a setup. Sometimes you might want to stopper one of the necks so that you can take samples from the reaction mixture or add portions of some reagent in a powdered form.

The extra necks aren't that useful if you want only to reflux something on a mag stirrer. But there is more to chemistry than RP/I and LWR. ;)


  • Guest
Traditional Gassing Setups
« Reply #3 on: September 05, 2004, 08:23:00 PM »
They're decent for traditional gassing setups where you drip sulphuric onto HCl saturated NaCl with an addition or sep funnel. If you've got any old version of Fester's SOMM there should be a simple diagram for it in there. Are all 3 necks 19/22?

Swim's buddy has a 4 necker with 3 24/40's and a central 34/45. He'd like to get one of those eurostyle three necked flat bottoms.

Here's a quite crude sketch of how a 3 necker might be used in a traditional gassing rig.


  • Guest
Re: Are all 3 necks 19/22? Yep!
« Reply #4 on: September 11, 2004, 06:19:00 AM »

Are all 3 necks 19/22?

Yep! I sure as hell aint gonna use it as a gasser. I mandate all gassing equipment must be disposable after each use. That is if I ever was to gas anything that was in need of dry hcl gas. ::)


  • Guest
Is there something im missing?
« Reply #5 on: September 11, 2004, 08:50:00 AM »
Is there something im missing? sulfuric acid is being dropped onto salt... and it states the salt is saturated with hydrochloric acid.
Do you pre soak your salt with HCL before dripping sulfuric onto it? is this the way its done in SOMM?


  • Guest
never tried it. Aluminum and muratic with a...
« Reply #6 on: September 11, 2004, 08:47:00 PM »
never tried it. Aluminum and muratic with a few gas traps and $2.39 worth of aquarium tubing , using left over H2O2 bottles for traps with cotton or paper towel stuffed in there to absorb moisture.

It's a tempramental reaction as a way to gassing and by far cant be the best.....but i've read that you need rock salt and pure sulfuric acid as opposed to battery electolyte replacement acid for this to work...? Right?


  • Guest
si senor
« Reply #7 on: September 13, 2004, 01:56:00 AM »


  • Guest
Alot of the time it is really only necessary...
« Reply #8 on: September 13, 2004, 02:41:00 PM »
Alot of the time it is really only necessary to use two necks. The third neck is not actually essential (depending on what you are doing), it even has the tendancy to annoy me when I dont make use of it. It is used for fancy things such as thermometer adaptor, pH adaptor and Cannula. Spiking the vessel with nitrogen also makes use of this third neck. 500 mL is a good figure to use. Mine is actually 1000mL with 24/29 joints. It does have a slightly manic presence though. Sometimes I feel like I quite literally have the globe in my hands!  :-[  :o  If you are going to be doing multiple gassings consider preparing a stock solution perhaps with some anhydrous MgSO4 added. My Yugoslavian neighbours said it is possible to use conc acid and that gassing really is not what you need to be doing if you can avoid it.


  • Guest
« Reply #9 on: September 13, 2004, 06:20:00 PM »
Are all three necks 19/22?

Quite simply NO.  I don't know of any piece of glassware that is only available in a single taper.  Not to say that such a piece of glass does not exist, but as far as three neck flasks are concerned they come in many different tapers and the necks themselves can be of different arrangements and shapes.




  • Guest
Ethyl, I have seen many three necked flasks...
« Reply #10 on: September 14, 2004, 09:03:00 AM »
Ethyl, I have seen many three necked flasks that had all the necks the same g/g size.

In fact these are the most common ones, IME.

Where necks are not a uniform size, you will usually find that the centre neck is bigger than the outer 2 in order to acommodate overhead stirrers.

Check here:

If this is a problem for matching other glassware, you can simply get adaptors to adjust the neck sizes.

Check here:

Chemosabe, I have had that diagram psychologically analysed and have come to the conclusion that you are a blood relative of John Wayne Gacy. :)


  • Guest
Reading Comprehension
« Reply #11 on: September 15, 2004, 02:38:00 AM »
Ethyl, I have seen many three necked flasks that had all the necks the same g/g size.

Yeah, so have I, own a few to boot.... I must not have comprehended that post correctly.  I read it as "Are all three neck flasks 19/22" i.e. is that the only taper that three neck flasks come in, not "Are all three necks on a three neck flask 19/22".  I thought the first was a strange question to be asked.  Turns out I just can not comprehend simple english.

I did not intend the post to be a flame by any means, in case someone got the wrong idea  ;)

In closing if you can dream it you can order it, as far as neck sizes, tapers, arrangement, or what have you, that was my point.




  • Guest
« Reply #12 on: October 26, 2004, 04:57:00 AM »
since this flask is a 19/22 flask, could one fit a 14/20 claisen or a 14/20 stillhead in it?

19/22 ? 14/20??

22 and 20 being what? the length #? or the diameter #?

I often ponder these things.


  • Guest
not interchangeable
« Reply #13 on: October 26, 2004, 11:46:00 AM »
LowJack, no, you cannot fit those joints together. Standard joint sizes take the form xx/yy where xx is the diameter of the wide end of the socket/cone, and yy is the length of the joint.
Even when joints of different sizes will mechanically fit together, it's a bad idea to use them like this as it leads to bad seals and stuck jointware.


  • Guest
one thing i always wonder about is the ...
« Reply #14 on: October 26, 2004, 02:51:00 PM »
one thing i always wonder about is the australia vs USA differnece....

we use 19/26 and 24/29 where as the american makers sell 19/22 and 24/40 (?) so i usually wonder if i buy USA stuff if it will be good enough for use with my aus gear....

Doubt it... esp for 24/40 your cone length is nearly double what we use.... but what about 19/26 or 19/22? ok or not? but i guess the american makers will make the size i want if asked....



  • Guest
They will fit, but as the joints are of ...
« Reply #15 on: October 26, 2004, 03:31:00 PM »
They will fit, but as the joints are of different lenghts there will always be ground glass surface well exposed to whatever conditions. I wouldn't try such a trick when doing a reaction with hot alkali, the exposed part of the ground glass joint could well get "polished".

You can also buy adapters if you wish to use the US joints with other standards.


  • Guest
glass adaptors are the way to go
« Reply #16 on: October 27, 2004, 02:39:00 AM »
It is quite amazing how many odd-sized (and often, quite strange-looking) pieces of glassware can be utilized together by using simple ground glass adaptors.
  If you do not have the luxury of going into your local scientific glassware supplier to pick out an adaptor try to find another source.
  Of course, no one should post any source here at the Hive (and for good reason), but you have the internet at your disposal. 
  Don't think too hard mmmkay?