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Thermodynamic Temperature

  1. Apr 11, 2013 #1
    Hello, new to these forums

    I'm trying to complete a basic thermodynamics problem, calculating the thermodynamic temperature of a gas immersed in water at triple point.

    The problem begins with a table of pressures at varying temperatures of a gas under pressure P, and pressure P(tp) - triple point pressure.


    Now, I know the following equation;

    T=LIMPTP→0P/PTP * 273.16

    So I have calculated the average value of P/PTP as 1.53555

    But I also have access to a solution to this problem, and in the solution an extra step is also taken:


    I don't understand the source of the 2.5 * avg change between P and P(tp). Where has this come from? Why is it necessary?

  2. jcsd
  3. Apr 11, 2013 #2

    Philip Wood

    User Avatar
    Gold Member

    I don't understand either, but rather than trying to do so, I've used a more straightforward method. I evaluated P/Ptp to 5 decimal places for each of the five pairs of readings. It was then clear that the ratio increased by almost the same increment for each 250 mmHg decrement in Ptp. Hence naïve extrapolation of P/Ptp to zero pressure is very straightforward.
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