Evaporation point for Ammonia?

-33.4°C (1013 hPa)

"David F. Eisan" wrote in news:Zlwrb.192973$ snipped-for-privacy@news04.bloor.is.net.cable.rogers.com:

-28 degrees F.

You'll be working with a dilute aqueous solution, and if that freezes, then it ain't going to happen...

I've also found that the reaction is annoyingly slow over Winter. I fume in daylight, rather than my usual leaving it overnight. A little heat might not hurt either - try a small lightbulb or cabinet heater.

-- Die Gotterspammerung - Junkmail of the Gods

The more important question is the rate of reaction of the ammonia with your wood. Generally speaking chemical reactions are slowed by *about* a factor of 2 per 10 degrees Celsius. So your instincts are correct, its probably the low temperature that's the problem, not because of the vapor pressure of the ammonia but because of the slower rate of reaction with the wood. Wait until you have warmer weather.

Partial pressure of the ammonia is also affected by the lower temperature (vapor pressure) of the water, isn't it?

Which law is that, Henry's?

LOL!

That means MAY!

djb

about. More likely you have a bottle of reagent grade ammonium hydroxide. If so, you aren't merely dealing with evaporation temperature but with how quickly this solution is freeing ammonia into the atmosphere under the tent.. But you will probably have to either raise the temperature substantially (10-15 degrees C would be my guess) or be willing to wait a very long time.

At even 0C ammonia must be kept under high pressure for it to remain liquid. Did your ammonia come in a highly pressurized cylinder with dire warnings all over it or in a bottle?

David the evaporation point isn't what you should be asking about. It is the vapor pressure of the ammonia/water solution that is biting you in the butt. A solution of 30% ammonia has a room temp (25°C) vapor pressure of approx 1 atmosphere. Below room temp the VP is lower than 1atm and less and less ammonia will evaporate the colder the solution is. There are 2 fixes to your problem. Heat the ammonia solution or use a stronger solution.

For more than you ever wanted to know on this subject see

HTH.

Art

Hello there,

I am using 26% ammonium hydroxide solution.

I have shut the garage door, and I will run the heater tonight to keep the garage at 10-15ºC. Come morning, I will use the remote opener for the garage and let the air clear before going in.

Thanks everyone for the help,

David.

There is no temperature dependancy in Henry's Law.

I'm pretty sure.

-JBB

You're right, but the concentration/partial pressure terms (dissolved vs. gaseous) ARE temperature dependent.

temperature

I tried fuming my quarter sawn white oak table a few days ago at 72 degrees. Nothing happened, so I even waited overnight (mid 60s) and still not much visible change. I was rather disappointed. I used Ammonium Hydroxide 28%. Poured about a pint of it into a glass baking dish. Most of it was evaporated by morning. Any suggestions?

On Sun, 09 Nov 2003 16:37:15 -0600, Dave Balderstone scribbled

David E. is in the Southern Ontario banana belt, so it might mean April. ;-)

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