| Abstract: |
We used a novel toroidal cross capacitor to measure accurately the dielectric polarizability e(p) (i.e., the dielectric constant) of helium, argon, nitrogen, methane, and carbon dioxide at T = 50 degrees C. The data extend up to 7 MPa (5 MPa for CO2) and may be useful for calibrating on-line, capacitance-based systems that are designed to measure the heating value of natural gas. The uncertainties of e, and p are <3 106 and (3.0 10-5 p + 84 Pa), respectively. We used the properties of helium calculated ab initio from quantum mechanics to verify that the cross capacitor deformed in a predictable manner under hydrostatic (gas) pressure. Thus, we avoided a common cause of systematic errors in measuring the dielectric constant of gases. |
