LAUSR

Abstract On-phase PVTx and two-phase (vapor-pressure) properties of complex quaternary water + n-octane + sodium dodecyl sulfate (SDS) + 1-propanol solutions have been measured in the liquid and vapor phases. Measurements were made for three solutions of following compositions: Solution-1: 0.2720 (H2O) + 0.5059 (n-C8H18) + 0.0777 (SDS) + 0.1449 (1-C5H11OH); Solution-2: 0.6220 (H2O) + 0.1555 (n-C8H18) + 0.0777 (SDS) + 0.1449 (1-C5H11OH); Solutoin-3: 0.0777 (H2O) + 0.6997 (n-C8H18) + 0.0777 (SDS) + 0.1449 (1-C5H11OH). The concentrations of the components are in mass percent. Measurements were made along 13 liquid and 3 vapor isochores between (336.7 and 911.6) kg·m− 3 over the temperatures range from (287.5 to 662.0) K and at pressures up to 36 MPa using a constant-volume piezometer technique. The combined expanded uncertainty of the density, ρ, pressure, P, and temperature, T, measurements at the 95% confidence level with a coverage factor of k = 2 is estimated to be 0.13%, 0.0002 MPa (for P   1 MPa), and 15 mK, respectively. The measurements were concentrated in the immediate vicinity of the phase transition temperature to precisely determine the phase boundary properties (PS , TS , ρS) on the liquid + gas equilibrium curve. The liquid-gas phase transition temperatures and vapor-pressures (liquid-gas phase boundary curves data, PS , TS , ρS) for the solutions were obtained using the isochoric (P-T) break point technique. The present results for phase-transition data are in good agreement with reported data obtained by calorimetric measurements. The effect of thermal decomposition (chemical reaction) on the measured values of vapor-pressure was studied.