Sciencemadness Discussion Board

Crystals at bottom of ammonia?

Godrick VanHess - 5-6-2020 at 14:18

So I have a bottle of household ammonia from many a year ago (Guessing about 6% ish) that has developed clear crystals at the bottom. They are extreamly fine needles that move freely. The bottle has been stored in the dark at 20 °C for atleast 7 years in a glass bottle with a steel lid with some sort of plastic inside coating. The lid has absoultly NO corrosion on it at all. I do not store it in the same room as any liquid acids. Has this ever happened to anyone before and if so any idea what is is? My best guess is it absorbed something from the air and precipitated an ammonium salt.

draculic acid69 - 5-6-2020 at 21:52

Is it cloudy ammonia that has had the soap settle out of it? If any atmospheric contamination occurred it would be ammonium carbonate. Most ammonium salts are fairly water soluble so not sure if that goes for an ammonia solution though.

Sulaiman - 5-6-2020 at 22:59

If there is still ammonia in solution then the vapor pressure would not have allowed atmospheric contamination,
So the crystals must be from the initial ingredients,
Based on a quick goole of SDSs, nonylphenyl ethoxylate seems to have been a commonly added surfactant.

Refinery - 6-6-2020 at 06:32

When I made ammonia by bubbling U+NaOH+H2O reactants into cold water, I noticed a faint amount of white precipitate at the bottom of the rec flask, which eventually dissolved. I presumed it was ammonium carbonate, because minor amounts of CO2 can be evolved from urea decomposition.

Bezaleel - 11-6-2020 at 03:31

It's a bit odd. I've noticed crystals at the bottom of old ammonia bottles as well and also wondered what they could be.

According to wiki, ammonium carbonate has a water solubility of 100g/100ml, meaning it is highly soluble in water. Can the addition of 5% of ammonia really have such high impact on the solubility of (NH4)2CO3? Unfortunately, periodic table of the elements does not give any further information.

Godrick VanHess - 12-6-2020 at 06:25

I would be shocked if it was ammonium carbonate. It seems far too soluble in water to crystallize out. The surfactant though maybe? It's a bit of a head scratcher to me. I am afraid I do not have a SDS for my ammonia solution and the ones I find don't list any surfactant but it very possibly changed since.

[Edited on 12-6-2020 by Godrick VanHess]

[Edited on 12-6-2020 by Godrick VanHess]

Godrick VanHess - 12-6-2020 at 06:34

Quote: Originally posted by Bezaleel  
It's a bit odd. I've noticed crystals at the bottom of old ammonia bottles as well and also wondered what they could be.

According to wiki, ammonium carbonate has a water solubility of 100g/100ml, meaning it is highly soluble in water. Can the addition of 5% of ammonia really have such high impact on the solubility of (NH4)2CO3? Unfortunately, periodic table of the elements does not give any further information.
When you say at the bottom of old ammonia bottles are we talking commercial ammonia or stuff you prepared? It would be so much more interesting if it was crystallizing from pure ammonia and not just the store bought crap.

Bezaleel - 15-6-2020 at 04:08

Quote: Originally posted by Godrick VanHess  
When you say at the bottom of old ammonia bottles are we talking commercial ammonia or stuff you prepared? It would be so much more interesting if it was crystallizing from pure ammonia and not just the store bought crap.

Just the bought stuff, not my distilled solution, and also only on very old bottles (5+ years). So it must be some kind of additive not specified on the bottle. I wouldn't rule out that it gets out of solution due to the winter-summer temperature cycle.

Refinery - 15-6-2020 at 04:23

It would be impossible to determine without testing, but ammonia could react with stuff in water that it was dissolved, or byproducts from ammonia generation, or from materials it were handled and packed with.

More of an interest is, will this mystery impurity cause issues when the ammonia is used for synthesis?