ARE THE INTEGRATED ABSORPTION-COEFFICIENTS TEMPERATURE-DEPENDENT - FT-NIR STUDY OF THE 1ST OVERTONE OF THE OH STRETCHING MODE OF OCTANOIC-ACID

The integrated molar absorption coefficients of the first overtone of an OH stretching mode of free octanoic acid were determined through a series of FT-NIR measurements in a CCl4 solution at different temperat ures. A few methods of calculation of the molar absorption coefficient were applied; the results were compared and discussed. It was shown t hat not all of the methods can be applied for the calculation if the p lot of Beer's law does not pass through the origin. The results clearl y show that the integrated molar absorption coefficient is strongly te mperature dependent; its value increases approximately 0.6 dm3 mol-1 c m-1 per one degree and the use of a constant value of the coefficient through a temperature range may lead to significant errors.