Sciencemadness Discussion Board

Ammonia from ammonium bicarbonate ?

Sulaiman - 30-8-2024 at 23:33

Ammonia solution is weak (typ. 3%) and expensive here,
so I bought ammonium bicarbonate (sold as a leavening agent for baking)
thinking that I could easily release ammonia
using either heat or a strong base, and dissolve it in water.
Unfortunately all paths I've found so far release CO2 as easily as NH3, so recombination is likely.

How can I selectively release ammonia or selectively absorb CO2. ?

Keras - 31-8-2024 at 00:30

NH₃ is basic and CO₂ is acid. Pass the mixture into a solution of concentrated sodium hydroxide. It will precipitate sodium carbonate and leave ammonia unchanged.

bnull - 31-8-2024 at 08:28

You can use calcium hydroxide. Make a sludge of calcium hydroxide in a round-bottom flask, add ammonium bicarbonate, mix and then heat it. Easy to clean, not too corrosive.

Or you can try a funnel instead (even the upper half of a soda bottle will do). Fit a filter paper to a funnel (a coffee filter in the case of the soda bottle), fill it with calcium hydroxide, and then pour a strong solution of ammonium bicarbonate over it. Calcium carbonate stays in the filter, a solution of ammonia passes through and can be purified. That's how I made some sodium hypochlorite from pool chlorine with sodium carbonate as filtration aid.

woelen - 31-8-2024 at 09:42

If you can get NaOH it is even simpler. Just mix solid NH4HCO3 and NaOH and add a few drops of water to start the reaction. Gaseous NH3 escapes (beware, the reaction is quite violent and somewhat exothermic) and Na2CO3 remains behind. A similar method of preparation is possible with NH4Cl and NaOH.

Sulaiman - 31-8-2024 at 22:47

@Keras, thanks. I didn't think of concentrated solutions
@bnull, excellent, thanks, but ...
@woelen, I like the idea, (I have sodium and potassium but not calcium hydroxide)
Is the reaction likely to melt HDPE ? (I guess yes)
I'll probably semi-sacrifice a glass rbf.

Thanks for answering my question :cool:
that I should have been able to answer for myself :P

woelen - 1-9-2024 at 10:29

What I did for this reaction is taking a simple small bottle from some booze (a small 100 ml bottle). I made a hole in the cap and put a PVC tube through it. This works quite well. I, however, did not manage to get a long term slow flow of NH3. It is fine for having a fairly strong flow of NH3 for a snort time. You'd better use such a bottle, than (semi-)sacrifice an expensive roundbottom flask.

Rainwater - 1-9-2024 at 15:14

Short of condensing the gas and storing it in a pressure vessel, get a big birthday balloon.

Sulaiman - 2-9-2024 at 03:05

Quote: Originally posted by Rainwater  
Short of condensing the gas and storing it in a pressure vessel, get a big birthday balloon.
my aim is to make and store ammonia solution.
Storing the gas is too troublesome.

SplendidAcylation - 2-9-2024 at 13:24

Perhaps you could make a solution of ammonium bicarbonate and add calcium chloride, precipitating calcium carbonate, filter, and evaporate the solution to obtain ammonium chloride, then act upon this with a strong base?

Rainwater - 2-9-2024 at 17:52

Quote: Originally posted by Sulaiman  
Quote: Originally posted by Rainwater  
Short of condensing the gas and storing it in a pressure vessel, get a big birthday balloon.
my aim is to make and store ammonia solution.
Storing the gas is too troublesome.


Using NaOH + NH3CO3
Quote: Originally posted by woelen  
I made a hole in the cap and put a PVC tube through it. This works quite well. I, however, did not manage to get a long term slow flow of NH3. It is fine for having a fairly strong flow of NH3 for a snort time

Use thus method and feed the results into a balloon.
Then strap the balloon over a bottle of water. Giving the gas time to dissolve

If you bubble the gas through water you will lose a lot of it.
Nerd rage has a video about these reactions. Explaning the methods used to generate the gas. I disagree with the collection method, tho.

Sulaiman - 3-9-2024 at 00:41

Ah, I get it now.
I misunderstood and thought that a balloon was suggested for long term storage.
An excellent idea
Thanks.

chloric1 - 3-9-2024 at 16:15

Quote: Originally posted by woelen  
What I did for this reaction is taking a simple small bottle from some booze (a small 100 ml bottle). I made a hole in the cap and put a PVC tube through it. This works quite well. I, however, did not manage to get a long term slow flow of NH3. It is fine for having a fairly strong flow of NH3 for a snort time. You'd better use such a bottle, than (semi-)sacrifice an expensive roundbottom flask.


I recently watched a YouTube video on an ammonia generator from Doug’s lab. Hey started out by adding concentrated ammonium sulfate solution to solid sodium hydroxide in a round bottom flask with a reflux condenser with a gas outlet adapter with tubing running into a graduated cylinder with water. His whole point was that ammonium sulfate and sodium hydroxide produced a byproduct that was liquid even at room temperature. That way after the ammonium sulfate addition was completed, you can easily apply heat to drive the rest of the ammonia out. If you have an empty bottle between gas outlet and water dissolution to prevent suckback, you could produce molar quantities of ammonia.