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# Vapour pressure of Ammonia: Ammonia solution under pressure2

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## Vapour pressure of Ammonia: Ammonia solution under pressure

(OP)
I have a system where aqueous ammonia is heated under pressure.
Solubility of ammonia drops from 33% at 0°C to 16% at 60°C at normal atmospheric pressure.
The system is under pressure of 10 bars.
Can I predict how much ammonia remain dissolved in solution?
If so, how?

### RE: Vapour pressure of Ammonia: Ammonia solution under pressure

Just find the water-ammonia phase diagram.

2

### RE: Vapour pressure of Ammonia: Ammonia solution under pressure

Aqueous ammonia equilibrium data is in Perry's too.

Good luck,
Latexman

Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers

### RE: Vapour pressure of Ammonia: Ammonia solution under pressure

(OP)
If my system is under 10 bars, and the vapour pressure of ammonia is 2 bars, how does the equilibrium work out?
Would one fifth of my ammonia turn into gas?

### RE: Vapour pressure of Ammonia: Ammonia solution under pressure

We really need more information on the system. Total volume, initial liquid volume, volume for vapor. What is providing the 10 bar of pressure?

Look at "Vapor Pressure of Solutions" in Perry's.

For a rough answer, usually the inventory in the vapor space of a closed system is negligible (it may not be in your case). If negligible, I would expect 33 wt. % liquid heated to 60 C to have a partial pressure of NH3 = about 4 bar (from Perry's). There would be a small partial pressure of the water that we could probably ignore. So, the liquid would still be about 33% and the vapor about 40% NH3. The other 60% in the vapor is whatever is providing pressure up to 10 bar.

For a more accurate answer, there would have to be a material balance of the two phases and interpolation of equilibrium data.

Good luck,
Latexman

Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers

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