Sciencemadness Discussion Board

Erlenmeyer Vacuum Flask

golfpro - 14-7-2013 at 17:05

Hi, what does a vacuum flask do in the process of bubbling a gas through solution? I have a set up that bubbles gas through a rubber tube into another solution but there is no vacuum anywhere. It is a glass jar w/ rubber tubing sealed off completely. For instance, copper dissolved in a nitric acid solution to produce NO2 gas which travels through the tubing and bubbles through water in another beaker which isn't sealed obviously. I want to bubble acetylene gas into a silver nitrate/nitric acid solution.

Although I have seen all of the liquid sucked from flask #2 back into the gas generating flask #1.

[Edited on 15-7-2013 by golfpro]

Variscite - 14-7-2013 at 18:49

Im confused by what you are asking. In the middle of a gas generating setup, a vacuum flask can act as a suckback preventor from what I know. rephrase your question if you can.

golfpro - 14-7-2013 at 19:58

So I had a glass jar with a hole on top for rubber tubing, then I epoxy sealed this to make it air tight, the copper reacting with HCl and AN solution creates NO2 gas which has nowhere to go but through the tube which sits in flask #2 and bubbles through this. I left it for about 3 hours and checked, it was doing good, checked 30 mins later, all liquid was sucked back into the original glass jar, I don't exactly understand how this happens, but the copper reacting with the acid generated a good bit of heat.

For what I would like to do later I would be present to not let the liquid be sucked back after all has bubbled.

Variscite - 14-7-2013 at 21:39

Nitrogen dioxide is highly soluble water, so if the flow of gas slows down, it causes water to violently suck back into the tube and the generator. The gas has such a high affinity for water it makes a back suction and will pull water unless you have a suck-back preventor, which can just be an empty flask with tube in a 2 hole stopper or a vacuum flask. Using an inverted funnel in the solution, attaching the tubing to the neck part and putting it into solution in a beaker is supposed to prevent suck-back into the gas gen.