Sciencemadness Discussion Board

Ammonia gas sucks water back up apparatus?

thehexlibrary - 28-5-2020 at 21:05

hi guys, thanks for taking the time to help me
I've been having this problem for awhile and can't figure out what to do. I'm running a reaction that generates ammonia gas in a classic distillation set up.
The ammonia gas runs through the glassware, into tubing, and into a beaker of water, where it can bubble through and generate an ammonia solution.
The problem is, after a couple seconds a bubbling, water starts getting sucked back up the tubing, and into the glassware.
I have no idea why this is happening, maybe the ammonia dissolving in the water creates a pressure difference that causes the water to move back up?

I kmow its supposed to be possible to bubble ammonia through a water solution, i just don't know how to fix this. Does anyone know a way to prevent water from flowing back through the setup when trying to bubble ammonia through?

B(a)P - 28-5-2020 at 21:18

Take a look here http://www.sciencemadness.org/talk/viewthread.php?tid=3836

thehexlibrary - 30-5-2020 at 10:45

thanks so much! upside down funnel seems to be the answer to my questions! will try it out and see how things work

draculic acid69 - 30-5-2020 at 18:51

Also putting a spaghetti sauce jar with two nipples in the lid between the gas source and the water absorption vessel helps prevent accidents. If I remember correctly the jar should be raised higher than the other two helps to prevent suckback.

IMG_20200531_124158.jpg - 525kB

thehexlibrary - 31-5-2020 at 06:34

draculic thanks so much! the pic is super helpful too! 'Preciate it!