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Author: Subject: dropwise addition for 8 hours
andre178
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shocked.gif posted on 26-1-2010 at 14:02
dropwise addition for 8 hours


Hello all,

I am working on a reaction that requires dropwise addition of reagent for 8 hours, what kind of glassware am I looking at setting up? How do I even google this type of setup?

Not sure where to begin with it!
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bahamuth
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[*] posted on 26-1-2010 at 14:13


You could try a addition funnel, and they come in a variety of sizes.

Just count drops per minute, 21 drops to the ml, and adjust it every 15min or so the first hour and then once an hour.

Have never done an addition for so long but this might do the trick.

Perhaps some of the more experienced chemists here have the know how.





Any sufficiently advanced technology is indistinguishable from magic.
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Lambda
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[*] posted on 26-1-2010 at 14:58


You are looking for a Step Motor Burette (or Motorburet), also called an Automatic Buret, which can also be pulsed. A simple 555 Timer IC Chip can do the pulsing job for you. Pulse time on/off duty cycle can easily be adjusted and calculated to your specific needs. You can also use a Syringe, driven by a worm wheel (DIY threaded rod and nut), driven by a slow turning synchronous motor (found in mechanical timers like those used in washing machines).

Step Motor Burette.pdf:
http://labfiz.uwb.edu.pl/labfiz/siec/info/dokumentacja_oeiiz...

Still Hanging on with Your Old Buret.pdf:
http://metrohmusa.com/utilities/download_pdf.asp?DR=download...

555 Timer IC:
http://en.wikipedia.org/wiki/555_timer_IC

Schematics and Links (copy and past this link into your browser):
http://images.google.nl/images?hl=nl&client=firefox-a&am...:official&hs=q2Z&q=ne555&um=1&ie=UTF-8&ei=GnJfS56zB8qw4Qbyx7X3Cw&sa=X&oi=image_result_group&ct=title&resnum=4& ved=0CCIQsAQwAw

Electronic Delay Timer Kits & Modules:
http://www.quasarelectronics.com/delay-timers.htm

The setup my then be turned off by means of a $5 to $10 dollar Digital AC Mains Timer, with or without a relay connected to it. You can then use an additional connected relay to switch low voltage appliances.

Digital mains timer socket 3 pack (far to expensive, even for a 3 pack):
http://www.amazon.co.uk/Digital-mains-timer-socket-pack/dp/B...

Lambda

[Edited on 26-1-2010 by Lambda]
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starman
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[*] posted on 26-1-2010 at 18:52


For the price of a pressure equalising dropping funnel you can pick up a small oem peristaltic pump.These are available in combinations of RPM and tubing sizes to provide addition rates down to a small fraction of a ml per minute.Various tubing types are available for just about any chemical you may handle.I put one together from components from under $80.



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andre178
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[*] posted on 27-1-2010 at 12:54


yep a peripump is what I got to use, the step motor burette is a nice idea just too technical and not user friendly :)


Thank you for the responses
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medchem
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[*] posted on 27-1-2010 at 17:10


for this purpose you can use "dropping funnel".

http://www.carl-roth.de/catalogue/catalogue.do?act=showBookm...

check out some images in the mentioned link.

good luck.




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