Speeds of Sound in n-Hexane and n-Heptane at Temperatures from (233.33 to 353.21) K and Pressures up to 20 MPa

Abstract

The speed of sound in high-purity n-hexane and n-heptane was experimentally studied utilizing the double-path length pulse-echo technique. Measurements with each alkane were carried out at temperatures from (233 to 353) K with pressures up to 20 MPa. Considering the uncertainty contributions from temperature, pressure, path-length calibration, pulse timing and sample purity, the relative expanded combined uncertainty (k = 2) in the speed of sound in n-hexane ranges from (0.012 to 0.042) % over the investigated ranges of pressure and temperature; for n-heptane, the uncertainty varies from (0.014 to 0.018) %. The sound speed data measured in n-hexane were among the data used for the development of a new fundamental equation of state, which is, however, not described in this work. The experimental data of n-heptane can be considered appropriate for modeling purposes and validation of existing equations of state.

Speeds of Sound in Methanol at Temperatures from 233.33 to 353.21 K at Pressures up to 20 MPa

“…The experimental procedure applied to conduct the speed of sound measurements in the scope of this work was adapted from previous works [59,60]. The stainless steel bottle containing the sample of methanol was attached to the evacuated speed of sound apparatus and carefully heated.…”

“…Speed of sound measurements in methanol were conducted employing the doublepath length pulse-echo technique with an apparatus according to the design of Meier and Kabelac [58]. The experimental set-up has been used for speed of sound measurements of several liquids in our previous works [59][60][61][62]; thus, it is only explained in brief at this point. A detailed description with illustrations of the measuring cell and a schematic drawing of the entire measuring system can be taken from the work of Gedanitz et al [63].…”

“…In order to avoid contact with the humidity of ambient air, the methanol sample was transferred to a stainless steel bottle within the dry inert argon atmosphere of a glove box that was manufactured in-house. Prior to use, the sample was degassed by repeated freeze-pump-thaw cycles, as described in our previous works [59][60][61][62].…”

“…The combined expanded uncertainty in speed of sound was estimated according to our previous studies [59,60], where the approach is explained in detail, by developing the following term with consideration of Eqs. (1) and (2):…”

Anomalous Phase Diagram and Conformational Behaviors of n-Hexane at High Temperatures and High Pressures

“…Until now, several research groups have studied the viscosity, sound velocity, refractive index, , thermal expansion coefficient, explosion characteristics, , combustion characteristics, and structural phase transitions , of n -hexane at high temperatures and high pressures. However, only a few reports have been published on the phase diagram of n -hexane at high temperatures and high pressures.…”