greenyppols
Hazard to Self
Posts: 97
Registered: 17-3-2005
Location: Behind you, watching intently, sexually tense.
Member Is Offline
Mood: Who's been messin' with my moods?
|
|
How to add solids to a sealed reaction
I've been researching how to carry out a reimer tiemann reaction.
A couple of sources mention an "apparatus that adds solids to a sealed system."
Near as I can figure they may be referring to a powder addition funnel, I did find a picture online but it was vague and not clear. It did not explain
its construction...
anyone know what this apparatus is, how its constructed or a pic of it?
Thanks
|
|
|
evil_lurker
National Hazard
Posts: 767
Registered: 12-3-2005
Location: United States of Elbonia
Member Is Offline
Mood: On the wagon again.
|
|
Professional glass manufacturers make addition funnels.
The work by having sort of a spring where the stopcock would normally be.
The spring acts as sort of a screw-feed mechanism much like a miniature auger.
I've only seen one on ebay. Expect to pay $$$ for a new one.
Here's a link to one:
http://www.aceglass.com/page.php?page=7239
[Edited on 5-10-2006 by evil_lurker]
|
|
|
not_important
International Hazard
Posts: 3873
Registered: 21-7-2006
Member Is Offline
Mood: No Mood
|
|
Another method, best for when it is OK to dump the solid in more or less all at once, is using a small flask and an angled connecting tube with male
joints an each end. The solid is put in the small flask, the tube used to connect it with the large flask at an angle that keeps the solid in the
small flask. To add, the connecting tube is rotated so the small flask is inverted and the solid falls from it through the connecting tube into the
reaction vessel.
The connecting tube isn't very common, but they show up in used equipment sales and are much cheaper than the nice powder-addition funnels.
|
|
|
matei
Hazard to Others
Posts: 205
Registered: 16-9-2006
Member Is Offline
Mood: No Mood
|
|
| Quote: | Originally posted by not_important
Another method, best for when it is OK to dump the solid in more or less all at once, is using a small flask and an angled connecting tube with male
joints an each end. The solid is put in the small flask, the tube used to connect it with the large flask at an angle that keeps the solid in the
small flask. To add, the connecting tube is rotated so the small flask is inverted and the solid falls from it through the connecting tube into the
reaction vessel.
The connecting tube isn't very common, but they show up in used equipment sales and are much cheaper than the nice
powder-addition funnels. |
You can find a picture in Vogel's 5th Ed. on page 82 (Figure 2.57).
|
|
|
mick
Hazard to Others
Posts: 338
Registered: 3-10-2003
Member Is Offline
Mood: No Mood
|
|
On an unknown reaction on an unkown scale that is brilliant advice. Dump the whole lot in and keep your fingers crossed. F... any exotherm. Most
reactions carried out under those conditions will be exothermic. Small scale, ie gram, no problem. A runaway exotherm on 100g can be serious. A
similar thing in a 100 gal pot blew the building to bits.
mick
Using polypropylene or polyethylene plastic sheet/bags and sellotape or similar you could make an inert gas (Argon or Nitrogen) tent.
edit mick
[Edited on 5-10-2006 by mick]
|
|
|
not_important
International Hazard
Posts: 3873
Registered: 21-7-2006
Member Is Offline
Mood: No Mood
|
|
@mick - I did say it was best when it is OK to add it all at once; that implies it shouldn't be used if the reaction does not fit that criteria. If
you've no idea how a reaction might run, then't you maybe should not run it at all or start real small and slowly scale it up. Plenty of people have
been hurt by adding X to Y slowly, only to be caught by a reaction that was slow starting, and finally took off after a lot of X had been added.
Note that not everyone has access to enough N2, let along argon, to run a tent over their entire apparatus; plus I've seen enough accidents from
tents interfering that I'd not use those as a blanket solution either.
@matie - thanks, the rubber tubing idea there allows a little more control on the addition. The second method looks interesting, if taking more work
to construct. Given that it is easier to get fabricated teflon these days, O-rings of fluorocarbon materials should make that useful even if fairly
nasty stuff is being handled.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
