[eds]

Hi everyone, just a random guy with a question here...

Is there any way of adapting Dalton's law on real gases? I am just wondering how to calculate partial pressures of gas mixtures inside a high pressure vessel.

[Radu]

  Yes, you can, but I don't know if it helps, anyway  . The relation is available for real gases, too.p=Σxip=x₁p + .   . On the other hand, maybe, you can derive a relation between the mixture fugacity and isolated fugacities of gases that mix, but with a correction factor, which weighs the A-B interactions. ( if you need something experimental)

   

[eds]

Thanks for the info Radu. It seems a bit too troublesome to calculate it actually. I'm just wondering why some gas mixtures like shielding gases, of which is commonly 75%, Ar 25% CO2, does not have its CO2 liquefy. I know it's usually by mixed by weight, but I'm trying to see if it is possible to calculate the real partial pressure of the CO2, as I want to know whether it liquefies inside the cylinder.

[Radu]

   So you want to calculate the fugacity of CO₂ in a mixture with Ar
  I think that a good approximation would be to treat Ar as a perfect gas ( at the melting temperatures of CO₂ it behaves perfectly).  You calculate (measure experimentally) the total fugacity( you experimentally measure Z of the mixture) and you take away the partial pressure of Ar(calculated as for a perfect gas), and you find CO₂ fugacity
    I just don't know how easy is to measure the mixture fugacity.... :-??