If you can smell Ammonia in the air, what would the equilibrium total ammonia concentration be in the tank water?

[taricha]

Let's make some (not good) assumptions to simplify things.

So I walked into the building where my tank is and my nose inspired the question...

If, in a room there is enough ammonia gas to smell, the aquarium skimmer has been running constantly, and the ammonia consumption by the system is small (we'll pretend zero) - what is the total ammonia in the tank water (pH 8.2, 77F) that would be in equilibrium with that smell-able concentration?

(I haven't tried to look up/work out the answer yet. )

 

[PharmrJohn]

I think it would be dependent on whether there is true dispersion (as in free floating, larger ammonia particulates) rather than a concentrated source separate from the tank. In my mind, a concentrated source would have no effect. It doesn't take much in the air to trip olfactory receptors. Whatever gaseous material secondary to a concentrated source would be eaten up by nitrifying bacteria in a heartbeat.

Now, if you were to put your tank in a cow barn, then enough methane from flatulence would get in the tank to kill it off. LOL, I've heard of larger cow barns igniting and, well, exploding. But hey! They are cows!

Just don't use a big spray bottle of Windex next to your tank!

 

[Randy Holmes-Farley]

I don’t think this is a look up question. It is very different for seawater vs fresh and will vary by pH, with a 0.3 pH unit drop in pH requiring twice as much concentration to smell the same.

 

[Dan_P]

Let's make some (not good) assumptions to simplify things.

So I walked into the building where my tank is and my nose inspired the question...

If, in a room there is enough ammonia gas to smell, the aquarium skimmer has been running constantly, and the ammonia consumption by the system is small (we'll pretend zero) - what is the total ammonia in the tank water (pH 8.2, 77F) that would be in equilibrium with that smell-able concentration?

(I haven't tried to look up/work out the answer yet. )

I would start with the detection limit of ammonia by humans of 5-53 ppb. Let’s pick 50 ppb and report our answers.

 

[BeanAnimal]

I would also think that vapor pressure, temp and humidity would have a lot to do with it.

 

[BeanAnimal]

I don’t think this is a look up question. It is very different for seawater vs fresh and will vary by pH, with a 0.3 pH unit drop in pH requiring twice as much concentration to smell the same.

Can you show where I can read about this? That very much is not something I know or would be intuitive at all for me.

 

[Miami Reef]

Maybe also the sensitivity of individual senses of smell can also come into play?

I personally was born with no sense of smell, so I have no idea what ammonia would smell like. I’ve never smelled a fart or anything like that either. Good or bad.

It’s always interesting to read about how people use their sense of smell in the world. It’s fascinating. I’ve never smelled gasoline, rotten food, or burning food on stoves, garbage etc. It’s all odorless to me.

 

[BeanAnimal]

Maybe also the sensitivity of individual senses of smell? I personally was born with NO sense of smell, so I have no idea what ammonia would smell like. I’ve never smelled a fart or anything like that either.

It’s always interesting to read about how people use their sense of smell in the world. It’s fascinating. I’ve never smelled gasoline, rotten food, or burning stoves. It’s all odorless.

Or steak - or cookies being baked, etc.

All of that means that you don't taste things the same as people with a sense of smell do. Wow.

 

[Miami Reef]

Or steak - or cookies being baked, etc.

All of that means that you don't taste things the same as people with a sense of smell do. Wow.

Steak has a smell?

I misspoke, my sense of smell is maybe 10-15% functional. I’ve faintly smelled cookies in the oven. It only works for VERY few things. And the things that I can smell is very muted.

I hate the smell of cologne/perfume/Febreze etc. it smells like a noticeable chemical. It’s not pleasant at all. It just smells like an anxiety attack (because I have trouble breathing when I get one).

 

[PharmrJohn]

Maybe also the sensitivity of individual senses of smell can also come into play?

I personally was born with no sense of smell, so I have no idea what ammonia would smell like. I’ve never smelled a fart or anything like that either. Good or bad.

It’s always interesting to read about how people use their sense of smell in the world. It’s fascinating. I’ve never smelled gasoline, rotten food, or burning food on stoves, garbage etc. It’s all odorless to me.

Can you taste?

 

[taricha]

Let’s pick 50 ppb and report our answers.

Agreed. Let's call it 50ppb in the air....

 

[Miami Reef]

Can you taste?

Yes. Many people say my food choices are weird. I like my food very plain. I detest spicy foods. They burn and don’t feel good. I don’t smell the food I eat. I rely on my taste.

I don’t know how my taste is compared to others, but you’ll never catch me saying, “wow, that smells so good I can’t wait to try it.”

 

[Dan_P]

Let's make some (not good) assumptions to simplify things.

So I walked into the building where my tank is and my nose inspired the question...

If, in a room there is enough ammonia gas to smell, the aquarium skimmer has been running constantly, and the ammonia consumption by the system is small (we'll pretend zero) - what is the total ammonia in the tank water (pH 8.2, 77F) that would be in equilibrium with that smell-able concentration?

(I haven't tried to look up/work out the answer yet. )

ChatGPT says for a water solution, and using the Henry’s law onstant for ammonia, you need a 3 micromolar solution (51 ppb or 0.051 ppm) to exert a pressure equivalent to 50 ppb. For your buffered saltwater aquarium, a larger amount must be absorbed before a sufficient amount of free ammonia exists to generate that pressure. If I take 0.051 ppm as free ammonia needed to generate that pressure by your aquarium, the total ammonia would be very approximately 0.51 ppm. I totally glossed over the effect on the pH.

I hope this was so off the wall that Randy will feel compelled to step in with the answer

 

[Randy Holmes-Farley]

I hope this was so off the wall that Randy will feel compelled to step in with the answer

The pKa of ammonia will be different (higher, easier to make NH4+) in seawater than in fresh. That's a complication, then pH is on top of that.

 

[BeanAnimal]

While we are waiting….

I don’t know about PPB or PPM but sticking my beak anywhere near a new bottle of this stuff is intense, if not rather uncomfortable.

 

[taricha]

ChatGPT says for a water solution, and using the Henry’s law onstant for ammonia, you need a 3 micromolar solution (51 ppb or 0.051 ppm) to exert a pressure equivalent to 50 ppb.

50ppb NH3 in air being in equilibrium with ~50ppb NH3 in water is the sort of chemistry relationship that feels pretty wrong, but sometimes isn't.
(not sure if I believe you yet or not)

 

[Randy Holmes-Farley]

Can you show where I can read about this? That very much is not something I know or would be intuitive at all for me.

THe vapor pressure of ammonia abve a water solution will be directly related to the NH3 concentration in the water (but not the same as it). Thus, salinity and pH and temp impact how much NH3 is in the air above an ammonia water solution.

 

[Dan_P]

50ppb NH3 in air being in equilibrium with ~50ppb NH3 in water is the sort of chemistry relationship that feels pretty wrong, but sometimes isn't.
(not sure if I believe you yet or not)

Physical chemistry is not my thing. I don’t believe me.

I suppose we could just keep adding ammonium chloride to seawater while keeping the pH constant until we smell ammonia. That would be sorta an answer. I would start at 10 ppm and make 10x jumps until I smelled something.

 

[BeanAnimal]

Ohh I think I see where pH comes into play, free ammonia. Took me a bit to catch on.

 

[Dan_P]

THe vapor pressure of ammonia abve a water solution will be directly related to the NH3 concentration in the water (but not the same as it). Thus, salinity and pH and temp impact how much NH3 is in the air above an ammonia water solution.

Got it. We could keep salinity and temperature constant and let the pH rise as NH3 is absorbed by the aquarium water in this thought experiment.