The speed of sound in n-octane and isooctane (2,2,4-trimethylpentane) was measured by the Brillouin light scattering (BLS) method. The examined regions for n-octane are T = (297–580) K along five isobaric lines at p = 0.1, 4.0, 7.0, 10.0, and 12.0 MPa for liquid and T = (573–673) K along ten isobaric lines with p = (3.0–10.0) MPa for supercritical fluid. The examined regions for isooctane are T = (294–525) K along five isobaric lines at p = 0.1, 3.0, 6.0, 10.0, and 12.0 MPa for liquid and T = (543–630) K along six isobaric lines with p = (3.0–10.0) MPa for supercritical fluid. The relative expanded uncertainty of the speed of sound is estimated less than 1.3%. Polynomial representations for the speed of sound in liquid n-octane and isooctane were fitted to the experimental results, respectively. The AADs are 0.27% for n-octane and 0.19% for isooctane. The influence of temperature and pressure on the speed of sound was also analyzed. Moreover, the data were also used to assess the predicted ability of three equations of state for n-octane.

中文翻译：

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液体和超临界正辛烷和异辛烷中声速的测量

通过布里渊光散射（BLS）方法测量正辛烷和异辛烷（2,2,4-三甲基戊烷）中的声音速度。对于被检查的区域Ñ辛烷是Ť =（297-580）K沿5条压线在p = 0.1，4.0，7.0，10.0和12.0兆帕用于液体和Ť =（573-673）K沿10的等压线与对于超临界流体，p =（3.0–10.0）MPa。为异辛烷被检查区域Ť =（294-525）沿五条压线■ p = 0.1，3.0，6.0，10.0和12.0兆帕用于液体和Ť =（543-630）K沿6条的等压线与p=（3.0–10.0）MPa（超临界流体）。声速的相对扩展不确定性估计小于1.3％。液体正辛烷和异辛烷中声速的多项式表示分别适合于实验结果。正辛烷的AAD为0.27 ％，异辛烷的AAD为0.19％。还分析了温度和压力对声速的影响。此外，该数据还用于评估三个状态方程对正辛烷的预测能力。