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Vapor Pressure Laws

  1. Jun 2, 2008 #1
    So, I'm new to astrophys, and I'm having trouble making a model because I don't think I understand an equation. It's a vapor pressure law, and it says it takes the form of

    log(pressure) = A-(B/T)

    T is in kelvins, A is 10.6, and B is 13500.

    Apparently pressure ends up being dynes/cm^2.

    So, first off, I don't know the units of A or B, or whether log is base ten or base e.

    In MatLab, I'm saying pressure = 10^(A-(B/T))

    Because I don't understand the equation, I don't know if that makes sense or not! Please help!
  2. jcsd
  3. Jun 4, 2008 #2
    You can find many vapor pressure formulae (for water) here:
    http ://cires.colorado.edu/~voemel/vp.html
    Equation [17] there looks the closest to your formula.
    Then the logarithm is natural and P is measured in Pascal.
    However, you may have the logarithm on the base 10 and pressure in hectoPascals.
    Pressure of what are you interested in? Is it actually water?
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