Talk:Ammonia

Image of ammonia (maybe liquid)

I think that an image should be added (given how important ammonia is), possibly similar to the pages for nitrogen or oxygen where the image shows the condensed liquid boiling. Sticklink (talk) 20:16, 24 January 2023 (UTC)

I've checked commons and the existing options are poor. Aqueous ammonia is a common laboratory reagent, so I don't think it would be too hard for someone to take a picture of a Winchester of it . Liquid anhydrous ammonia is trickier and also not very impressive to look at (clear colourless liquid - dull). The only way to make it interesting is to drop a shard of sodium in to make it look like this Project Osprey (talk) 21:48, 24 January 2023 (UTC)

ammonia angle

The article indicates that the same source indicates two different H-N-H angles: ... with an experimentally determined bond angle of 106.7° and ... therefore the bond angle is not 109.5°, as expected for a regular tetrahedral arrangement, but 106.8°.

As far as I know, both angles are wrong. In all the literature, I know (e.g. C.E. Mortimer und U. Müller: Chemie – Das Basiswissen der Chemie, page 130), I just saw that it's 107.3°. Can someone confirm that? FailXD (talk) 17:02, 5 September 2023 (UTC)

LD50

The LD50 is given as 0.015 ml per kg, which is far too low. The figure 0.015 would make sense if it referred to ml of liquid ammonia, or mg of ammonia, but not ml of gaseous ammonia. Someone knowledgeable in editing chemboxes should correct this to mg per kg or indicate that it refers to liquid ammonia, rather than the gaseous form ammonia has under standard conditions. Ammonia gas is about 1000 times less dense than liquid ammonia. The ICSC0414 data sheet cited farther down in the chembox gives a permissible level of 14 mg per cubic meter, which is equivalent to 0.014 mg per ml. CharlesHBennett (talk) 22:47, 3 February 2024 (UTC)

I wasn't able to find a human LD50 and the permissible level isn't really equivalent. I substituted a rat oral LD50 from a gas supplier SDS. Reconrabbit 19:28, 19 April 2024 (UTC)

Flash point

Most sources agree that ammonia does not have a traditional flash point, as it is a gas a standard temperature and pressure and the definition of flash point relies on the temperature at which liquid fumes become flammable. What is currently listed is the critical temperature, which is the temperature above which ammonia cannot form a liquid. The more relevant standard for ammonia flammability would be the lower explosive limit, which is the concentration in air at which ammonia becomes ignitable. 2601:281:8000:78E0:309D:DD9D:FB1F:A521 (talk) 18:34, 19 April 2024 (UTC)

It looks like the explosive limit is already listed at 15.0%-33.6%. Reconrabbit 19:27, 19 April 2024 (UTC)

"Liquid ammonia"

The Liquid section had a sentence that stated the liquid could be carried around a lab without refrigeration or a pressure vessel. This seems very unlikely considering that even with its high enthalpy of vaporization every source I can find says that liquid anhydrous ammonia vaporizes when exposed to air. I changed the section to reflect this - did it mean aqueous ammonia? Reconrabbit 20:16, 19 April 2024 (UTC)

Liquid ammonia, like every liquid, requires energy to evaporate. This energy can come from the surrounding environment, like from air, water, a flame, an electric heating element, etc., or from the liquid itself, such as when the pressure of compressed, liquid ammonia is reduced, it will evaporate and cool down, because its heat is used to evaporate itself. So, yes, liquid ammonia will evaporate if it's in an environment that's warmer than its boiling point of -33 C (at 1 atm, I guess), including air. But the rate of evaporation depends on the rate of heat transfer. In a well insulated dewar this will be slow, but if you mix it well with lots of air by spraying it into air, it will be fast. Intermediately, e.g. in a test tube it will evaporate, but slow enough to carry it around in a lab. The vapors are pungent and even lethal in sufficient amount, so don't inhale them too much. Here's a video where nilered is handling liquid ammonia he created: https://www.youtube.com/watch?v=gHokrNS1ask&t=535s

In a pressurized container liquid ammonia may be at ambient temperature at the corresponding vapor presssure, e.g. 1003 kPa (10.03 bar) at 25 C (Ammonia (data page)#Vapor–liquid equilibrium data). Opening a valve, especially below the liquid surface, will eject liquid ammonia due to its pressure. Outside the container the vapor pressure of ammonia (10 bar) is now above ambient pressure (~1 bar), so it flash evaporates instantly. As mentioned, this evaporation requires energy, which comes from the ammonia itself now. It cools down instantly, cooling down, and if the ammonia wasn't hot enough (have enough energy) in the container, it will cool down to its boiling point corresponding to the ambient pressure (-33 C) where some ammonia will remain liquid till it absorbs the remaining energy needed for full evaporation from the environment. If you're not in a position to shut the valve quickly, run (upwind)!

I guess the sources you found were about this flash evaporation, where all or most of liquefied, pressurized ammonia evaporates instantly. This is mostly due to exposure to lower pressure rather than to exposure to air.Darsie42 (talk) 13:35, 4 May 2024 (UTC)

We use liquid ammonia with no external cooling. In fact, in our teach lab, I insisted on not using coolants, which condense water that can kill sodium-ammonia. Arthur Birch's group (Birch reduction) measured out ammonia with big graduated cylinders. It's a little weird but the heat of evaporation is so high that these operations work fine. We just dont remove the thick crust of frost that collects on the containers.--Smokefoot (talk) 14:30, 4 May 2024 (UTC)

That's interesting to hear! If I've mischaracterized liquid ammonia in the article based on the sources then please correct me; I have never once seen liquid ammonia handled at my institution outside of the aqueous form. Reconrabbit 15:15, 4 May 2024 (UTC)