H214 Observation of Diffusion Phenomena in Ethanol Aqueous Solutions using Near-infrared Absorption Characteristics

Abstract

This paper presents a simultaneous imaging method of the temperature and concentration of ethanol aqueous solutions in a microchannel. Absorbance images at the two wavelengths in the ν_2 + ν_3 absorption band of water: 1905 nm and 1935 nm, are simultaneously acquired and converted to the temperature and concentration images. The absorbance at 1905 nm is the most sensitive to the temperature in the band, but that at 1935 nm is insensitive, i.e., an isosbestic point. Whereas, the absorbances at both wavelength are highly sensitive to the water molar fraction, which is inversely proportional to the ethanol concentration. When a 2 wt% ethanol aqueous solution and pure water meet and diffuse to each other, changes in the concentration are observed, and the temperature dependence of the diffusion coefficient is discussed.