No abstract

On the basis of the direct visual observation of the meniscus disappearance and reappearance in an optical cell, 17 saturated liquid densities and 8 saturated vapor densities of dimethyl ether were measured in the temperature range from 301.816 K to the critical temperature, corresponding to a density range from (66.75 to 654.54) kg·m-3. The maximum uncertainties of the saturated liquid and vapor densities are ±0.15 kg·m-3 and ±0.10 kg·m-3, respectively. The uncertainties of temperature were estimated to be within ±5 mK. The critical temperature T c and density ρc were determined as (400.378 ± 0.005) K and (272 ± 2) kg·m-3 by taking into consideration the meniscus disappearance and reappearance as well as the intensity of the critical opalescence. The critical pressure was (5356 ± 10) kPa extrapolated from the vapor pressures data with the Wagner equation. We have also determined the critical exponent β and the critical amplitude B on the basis of a correlation of the vapor−liquid coexistence curve.