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Antoine equation for D2O and D2O diffusion measured by a QMS

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chico-03:
Hello,

Currently working with deuterium oxide (D2O), I have some questions about the behaviour of this substance.


* I was trying to calculate the vapour pressure corresponding to a given temperature for D2O. That's possible for water thanks to the Antoine equation. When I looked for the parameters A, B and C for D2O, they were equal to zero. Why, knowing that the behaviour of D2O is not so far from the one of water? And what is the meaning of parameters of Antoine equation equal to zero?
* In a vacuum system, when diffusing D2O through a film and measuring the current on the other side with a quadrupole mass spectrometer, the mass 19 is always higher than the deuterium oxide, regardless of the time of pumping before. Any  idea of why this happens?
Any suggestion is welcome!
Thank you

Borek:

--- Quote from: chico-03 on September 13, 2022, 03:38:05 AM ---That's possible for water thanks to the Antoine equation. When I looked for the parameters A, B and C for D2O, they were equal to zero.
--- End quote ---

Where did you found them?

In many databases zero means "we have no idea what the real value is, but we have to put something here".

chico-03:
Thank you for your answer, that's good to know.

It was a physical property data bank found on Elsevier.

Enthalpy:
https://webbook.nist.gov/cgi/cbook.cgi?ID=C7789200&Mask=4
https://webbook.nist.gov/cgi/inchi?ID=C7732185&Mask=4

chico-03:
Thank you a lot for the links Enthalpy.
I forgot to mention that I'm working between 20 and 50°C and Liu and Lindsay start only at 106°C.

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