In the present study, the simultaneous and accurate determination of liquid viscosity and surface tension of the n-alkanes n-hexane (n-C6H14), n-octane (n-C8H18), n-decane (n-C10H22), and n-hexadecane (n-C16H34) by surface light scattering (SLS) in thermodynamic equilibrium is demonstrated. Measurements have been performed over a wide temperature range from 283.15 K up to 473.15 K for n-C6H14, 523.15 K for n-C8H18, and 573.15 K for n-C10H22 and n-C16H34. The liquid dynamic viscosity and surface tension data with average total measurement uncertainties (k = 2) of 2.0 and 1.7% agree with the available literature and contribute to a new database at high temperatures. Over the entire temperature range, a Vogel-type equation for the dynamic viscosity and a modified van der Waals equation for the surface tension represent the measured data for the four n-alkanes within experimental uncertainties. By also considering our former SLS data for n-dodecane (n-C12H26) and n-octacosane (n-C28H58), empirical models for the liquid viscosity and surface tension of n-alkanes were developed as a function of temperature and carbon number covering values between 6 and 28. Agreement between these models and reference correlations for additional selected n-alkanes, which were not included in the development procedure, was found.

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The liquid viscosity, surface tension, and liquid density of the two branched alkanes 2-methylnonane and 4-methylnonane were studied for temperatures between 283.15 and 448.15 K. The surface tension and liquid dynamic viscosity were obtained from surface light scattering (SLS) measurements close to saturation conditions with average relative expanded uncertainties (k = 2) of 1.5 and 0.9 %. Two vibrating-tube densimeters were used for the measurement of the liquid density at atmospheric pressure with relative expanded uncertainties (k = 2) between 0.01 and 0.5 %. The measured data could be correlated mostly within their expanded uncertainties by appropriate equations. Comparison with the few available literature data shows good agreement.

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