This Demonstration models the behavior of a sealed, 1-L autoclave that initially contains mostly water plus a small volume of air, all at 25°C. The initial volume of water is changed with a slider, and the temperature resets to 25°C when the initial water volume is changed. As the temperature increases by moving the slider, liquid water expands and its saturation pressure increases. At the same time, the gas-phase volume decreases, so gas-phase O2 and N2 partial pressures increase (ideal gas law). The amounts of O2 and N2 dissolved in the water increase with pressure, but decrease with temperature. The amounts dissolved are shown in the bar chart (green = gas phase, purple = dissolved). Even at moderate temperatures, the pressures inside the sealed container can be quite high.
The final liquid volume 
of water is given by:
,
where 
is the initial liquid volume (L) at 25 °C, 
is temperature (°C), and 
, 
, 
and 
are constants.
The total pressure 
in the container is equal to the saturation pressure of water 
plus the partial pressures of oxygen 
and nitrogen 
:
.
The saturation pressure of water is calculated using the Antoine equation:
,
where 
, 
and 
are Antoine constants.
The partial pressures of oxygen and nitrogen are calculated using the ideal gas law:
,
where 
is the fraction of oxygen or nitrogen in air where 
and 
, 
is the moles of 
in the gas phase, 
is the ideal gas constant ([L bar]/[mol K]) and 
is the vapor volume (L).
The total moles of oxygen 
and nitrogen 
in the container are calculated at 25 °C and 1 bar pressure, the moles in the gas phase are calculated using the ideal gas law, and the moles dissolved in water are calculated using Henry's law:
,
,
where 
and 
are Henry's law constants (mol/[L bar]):
,
.
For all and , the moles in the gas phase and dissolved must equal the total moles at 25 °C and 1 bar:
,
.