Densities of two methane-rich binary mixtures were measured in the homogeneous liquid and the supercritical region at temperatures between (100 and 160) K using a low-temperature single-sinker magnetic-suspension densimeter. For each mixture, four isotherms were studied over the pressure range from (0.3 to 10.8) MPa. Molar compositions of the gravimetrically prepared methane-rich binary mixtures were approximately 0.01 butane and 0.02 isopentane, respectively, with the balance being methane. The relative expanded combined uncertainty (k = 2) of the experimental densities was estimated to be in the range of (0.02 to 0.06) %. Due to a supercritical liquefaction procedure and the integration of a special VLE-cell, it was possible to measure densities in the homogeneous liquid phase without changing the composition of the liquefied mixture. Based on the supercritical liquefaction procedure, a new time-saving measurement procedure was developed and applied. Moreover, saturated-liquid densities were determined by extrapolation of the experimental single-phase liquid densities to the vapor pressure calculated with an equation of state (EOS); here, the relative expanded combined uncertainty (k = 2) is less than 0.05 % in most cases. The new experimental results were compared with the GERG-2008 equation of state, the EOS-LNG and the enhanced revised Klosek and McKinley (ERKM) method.

中文翻译：

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(0.99 甲烷 + 0.01 丁烷) 和 (0.98 甲烷 + 0.02 异戊烷) 在 (100 到 160) K 的温度范围内和压力高达 10.8 MPa 的密度测量

两种富含甲烷的二元混合物的密度在均质液体和超临界区域中在 (100 到 160) K 之间的温度下使用低温单沉磁悬浮密度计测量。对于每种混合物，在 (0.3 到 10.8) MPa 的压力范围内研究了四个等温线。重量法制备的富含甲烷的二元混合物的摩尔组成分别约为 0.01 丁烷和 0.02 异戊烷，余量为甲烷。实验密度的相对扩展组合不确定度 (k = 2) 估计在 (0.02 到 0.06) % 的范围内。由于超临界液化程序和特殊 VLE 单元的集成，可以在不改变液化混合物的组成的情况下测量均相液相中的密度。基于超临界液化程序，开发并应用了一种新的省时测量程序。此外，饱和液体密度是通过将实验单相液体密度外推到使用状态方程 (EOS) 计算的蒸气压来确定的；在这里，在大多数情况下，相对扩展组合不确定性 (k = 2) 小于 0.05%。新的实验结果与 GERG-2008 状态方程、EOS-LNG 和改进的 Klosek 和 McKinley (ERKM) 方法进行了比较。在大多数情况下，相对扩展组合不确定度 (k = 2) 小于 0.05%。新的实验结果与 GERG-2008 状态方程、EOS-LNG 和改进的 Klosek 和 McKinley (ERKM) 方法进行了比较。在大多数情况下，相对扩展组合不确定度 (k = 2) 小于 0.05%。新的实验结果与 GERG-2008 状态方程、EOS-LNG 和改进的 Klosek 和 McKinley (ERKM) 方法进行了比较。