[ayl08]

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?

[Schrödinger]

I think you can, using Henry's law. Although the law is stated for constant Temperature conditions, you should be able to incorporate the temperature dependence of the Henry's constant into the equation. There is a small sub section on this in wikipedia