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In every thermodynamics textbook there are tables containing the specific volume of various fluids at different temperatures and pressures. My question is, how is this data obtained experimentally?

I can imagine that this could be done with a piston arrangement where a known mass of the substance is placed inside, a known pressure is applied and the whole system is heated to a specific temperature. The specific volume could then be measured, giving an experimental data point. However, I was not able to find any reference to state if this is actually the most accurate method available.

Could anyone share any information on the apparatus and method that is used to accurately measure the specific volumes of fluids?

Thank you

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  • $\begingroup$ How would you go about measuring the density of some fluid? Once you know one you know the other because density and specific volume are reciprocals of one another: $\rho \nu = 1$. $\endgroup$ – David Hammen Dec 28 '14 at 11:06
  • $\begingroup$ Thanks for the hint, it pointed me in the right direction and I was able to find details of modern methods to measure gas densities. I will post a useful reference in an answer to this question. $\endgroup$ – Appguy1 Dec 28 '14 at 12:11
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Thanks to David Hammen for pointing me in the right direction. I was able to find some information on modern methods to measure gas densities.

The most accurate modern method is the Magnetic Levitation Densimeter, which works by suspending a weight from a balance plate using magnetic forces. The gas whose density is to be measured is then introduced to the chamber at a known pressure and temperature. By Archimedes Principle the weight measured by the balance changes. This change is then used to calculate the density of the gas.

A good reference is a PhD thesis that is publicly available, which explains this and several other density measuring devices in more detail:

http://repository.tamu.edu/bitstream/handle/1969.1/ETD-TAMU-1903/ATILHAN-DISSERTATION.pdf?sequence=1

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  • $\begingroup$ Elegant. Simple but powerful. $\endgroup$ – dmckee Dec 28 '14 at 22:05

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