0_8310 Structural and optical properties of various liquid species are of particular importance for both chemical and biological applications. These characteristics can be readily obtained from highly accurate, non-destructive ellipsometric measurements in a wide wavelength range. However, for a reliable result certain technical obstacles must be eliminated for this type of measurements, e.g., excluding the environmental vibrations and providing an aligned liquid surface are both essential. Previously, it was shown that by using an ellipsometric configuration with active pneumatic isolators it is possible to obtain vital structural information from both liquid-air and liquid-liquid interfaces revealing nanoscale surface structures [1].In this study the extended capability of the above method is presented for which the available wavelength range is increased toward the mid-IR region (ca. up to 15 mm). This wavelength domain is of great significance for revealing the chemical composition of the investigated liquid sample in a label-free manner [2], thus besides the structural and optical properties, additional information regarding the composition can also be measured. The capabilities of the proposed ellipsometric configuration are demonstrated with real measurements on bulk liquid samples, e.g., high purity distilled water, glycerol, PDMS solutions.