Sciencemadness Discussion Board - Interesting way to dissolve gasses into liquids without bubbling!

Interesting way to dissolve gasses into liquids without bubbling!

RogueRose - 25-4-2018 at 23:18

So JJay gave me an idea when he was talking about boiling down his calcium acetate solution under vacuum from an aspirator. I recently was trying to extract all the ammonia from a solution made from ammonium sulfate and Ca(OH2) and found it difficult to filter out the CaSO4 as it would pull the NH3 out of solution and into the vacuum.

Well we all know that the way to make ammonia solution is to bubble ammonia gas through water and this led me to think about the above statement by JJay. What better way to kill 2 birds with one stone and that is to boil the ammonia off at reduced temps and reduced pressure while at the same time not having to worry about the entire bubbling apparatus!

What I'm envisioning is either a filtering flask w/ hose connected to it and stoppered shut, or a regular flask with a a hose connector in the stopper. Then attack the hose to a closed circuit pumping system (they make pumps that do 4-6 LPM @ 90-125PSI that are $10-25) as well as sealed reservoir, and use the vacuum to absorb all the NH3 that is produced.

The more I think about this, I think this setup could be done with any setup where gasses need to be bubbled, like the production of HCl. The best thing is that it is all done under reduced pressure and lower temps than normal and only minimal heat is needed if any at all, depending on the compound!

Now the only issue that I can see is a reaction between the pump and the chemicals, especially the HCl. IDK how these pumps are made, but I would suspect that some of these would be able to handle ammonia very well but HCl might be pushing it. If the pump head is plastic, then maybe this is all very workable. I'm now looking to order a pump and see how it is made.

I also think it would be possible to have a unique pump head made from a block of PTFE and a CNC machine. I've seen some guys online playing around with machining PTFE and it is a beautiful material to work with in this manner, it has been compared to in between 6061 or 6063 Al and maple wood, both are very nice to work with on a lathe or CNC, so this seems interesting IMO.

Can anyone think of any issues in a setup like this or give ideas on fixing the pump issue?

Ubya - 26-4-2018 at 01:14

might work but i'm not really sure. any gases absorbed in the recirculating water of the pump will escape as the pressure lowers inside the pump, you won't get a vacuum as good as with pure water. now i'm just speculating, but there will be a point where the pump won't suck gas anymore because at a certain concentration gases will simply go out of solution at the same time as going in, but being in a reduced pressure you would reach this equilibrium at a lower concentration than doing this at atmospheric pressure

RogueRose - 26-4-2018 at 02:00

Quote: Originally posted by Ubya

might work but i'm not really sure. any gases absorbed in the recirculating water of the pump will escape as the pressure lowers inside the pump, you won't get a vacuum as good as with pure water. now i'm just speculating, but there will be a point where the pump won't suck gas anymore because at a certain concentration gases will simply go out of solution at the same time as going in, but being in a reduced pressure you would reach this equilibrium at a lower concentration than doing this at atmospheric pressure

AHHH! That is an excellent point that I hadn't thought of. I think this might be able to be gotten around by the type of pump head used, such as a peristaltic pump where there really is no vacuum formed, also maybe something like a turbine pump. I'll have to look into the different types of pumping action and see which one would produce the least amount "vacuum" on the working fluid and more of a continuous push/pull effect on it. I think that would be a way to remedy the issue of gassing out of the liquid. Does that sound plausible?

Thanks for the thought!

PhenethylamineMachine - 26-4-2018 at 05:34

Interesting stuff.

I was reminded of how in many procedures you will have the free-base of a compound dissolved in solvent and chilled to 0°, at which point hydrogen chloride gas would be bubbled into the solvent containing the free base, generally things are allowed to stand for a period of time at 0°c, and the hydrochloride salt of the compound will precipitate out, and can then be filtered-off and collected. It's pretty common in phenethylamine chemistry.

...Pretty creative thinking on your part though, which is a step towards progress and improvements of known procedures. Do not ever be afraid to explore new ideas, even if they do not work out.

Ubya - 27-4-2018 at 02:25

Quote:

mh but the problem still remains, i mean, how are you going to make a vacuum? using a water aspirator kind of pump? a water aspirator uses the venturi effect, the gases get stripped by a fast jet of water, so gases are in contact with the water, and the eater is in contact with the vacuum, that's what i meant

zed - 28-4-2018 at 15:42

Back in the day, Brown discovered that stirring a solution with an ordinary magnetic stir bar, produced pretty good gas entrainment. Good enough to run very efficient hydrogenations, at ordinary pressures and temperatures.

By utilizing a plastic sheathed, neodymium super magnet, I can really work up a froth so to speak. Sucks gas down through a central vortex, and blows out bubbles throughout the liquid phase. Provided, you keep the temperature down. Superior magnetic coupling, at least, when coolish. At ~80c, the magic ceases to work.

https://www.supermagnete.de/eng/faq/What-temperatures-can-ma...

[Edited on 28-4-2018 by zed]

VSEPR_VOID - 28-4-2018 at 23:04

Could you draw us a diagram? MS paint works well for simple things

zed - 2-5-2018 at 13:11

https://www.youtube.com/watch?v=JFNtP2N2Eho

http://courses.chem.psu.edu/chem36/experiments/exp131.pdf

These are small scale examples, but the Brown Method works for hydrogenating Liter quantities, equally well.

I have several wands, which work very well, as I recall. Just don't know when I will be using them again. https://www.fishersci.com/shop/products/pyrex-gas-dispersion...

Like others, I do have a situation, I can't figure out. I have a pressure vessel, with walls so thick, that magnetic stirring is not an option. Pumping, I have considered, but I haven't found a safe, easy option.

[Edited on 2-5-2018 by zed]

[Edited on 2-5-2018 by zed]

[Edited on 2-5-2018 by zed]