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ZachWeiner
Jun2-08, 10:35 PM
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!

avalonme
Jun4-08, 07:28 PM
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?