Viscosity and Surface Tension of Benzene at Saturation Conditions from Surface Light Scattering

Manuel Kerscher,Thomas M Koller,Andreas P Fröba

doi:10.1007/s10765-021-02909-7

Manuel Kerscher, Thomas M Koller + Show 1 more

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https://doi.org/10.1007/s10765-021-02909-7

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Abstract

In the present study, the liquid viscosity and surface tension of benzene was determined at saturation conditions from surface light scattering (SLS) experiments between (283 and 393) K. Based on the application of the hydrodynamic theory for surface fluctuations at the vapor–liquid phase boundary which was successfully validated by the measurements, a simultaneous determination of liquid viscosity and surface tension with average relative expanded uncertainties (k = 2) of (1.0 and 0.8)% was achieved. Agreement between the measurement data and reference values available in the literature was found for the viscosity and in general also for the surface tension, where benzene constitutes a recommended reference material of relatively moderate surface tension values. All these findings demonstrate for a repeated time that SLS is a suitable method for the investigation of fluids including reference fluids such as benzene, which enables a sound representation of its surface tension, presumably as a result of a rather random molecular orientation at the surface. Overall, the experimental results from this work could contribute to an improved data situation for benzene, in particular with respect to providing viscosities and surface tensions at true saturation conditions.

Highlights

Surface light scattering (SLS) is a well-established technique for the measure‐ ment of viscosity and surface or interfacial tension of fluids [1–3]
For an accurate determination of viscosity and surface tension, both of which can be accessed simultaneously in particular in the case of low-viscosity fluids, it is necessary to apply an exact treatment of the hydrodynamic theory for surface fluctuations [4, 5], whose wave numbers probed in the experiment should be sufficiently large [1, 6]
Larger relative differences between the different literature sources of up to 5 % are present, where the SLS results are in the lower band, but still agree satisfactorily with recommended reference values

Summary

Introduction

Surface light scattering (SLS) is a well-established technique for the measure‐ ment of viscosity and surface or interfacial tension of fluids [1–3]. The method probes the dynamics of thermally excited fluctuations at phase boundaries by the study of the intensity of the scattered light, which allows to perform meas‐ urements at macroscopic thermodynamic equilibrium in a contactless manner without the need for any calibration procedure. For an accurate determination of viscosity and surface tension, both of which can be accessed simultaneously in particular in the case of low-viscosity fluids, it is necessary to apply an exact treatment of the hydrodynamic theory for surface fluctuations [4, 5], whose wave numbers probed in the experiment should be sufficiently large [1, 6]. In the context of thermophysical property research, SLS has been applied for the measurement of viscosity and surface tension of various types of working fluids in process and energy engineering [2]. SLS investigations on the reference fluids toluene [1, 6] and diisodecyl phthalate [18] contributed to the development of standards of low viscosity [19] and moderately high viscosity [20]

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