INFRARED INTENSITIES OF LIQUIDS .13. ACCURATE OPTICAL-CONSTANTS AND MOLAR ABSORPTION-COEFFICIENTS BETWEEN 6500 AND 435 CM(-1) OF TOLUENE AT 25-DEGREES-C, FROM SPECTRA RECORDED IN SEVERAL LABORATORIES

This paper presents accurate infrared absorption intensities of liquid toluene at 25 degrees C. The accuracy is estimated from the agreement between the intensities measured by different spectroscopists using the same instrument in the same laboratory and also by different spectroscopists in different laboratories using instruments made by different manufacturers. The average agreement between integrated intensities over specific wavennmber ranges is about +/-1.8%. The spectra from the different laboratories have been averaged, unweighted, to give intensity spectra of toluene that are presented as the best available. The use of data from different instruments in different laboratories has included the influence of systematic instrumental errors, so that the precision of the intensity data presented should be a better approximation to its accuracy than would be the case from an extensive study by one person on one instrument. The results obtained agree with the only measurements that have been made against a primary standard, the estimated accuracy of which is about 6%. The results are presented as graphs and tables of the molar absorption coefficient spectrum and the real and imaginary refractive index spectra between 6500 and 435 cm(-1). The peak heights and the areas under the bands in the imaginary refractive index (i.e., absorption index) and molar absorption coefficient spectra rue reported. The absorption index, k(($) over tilde nu), and molar absorption coefficient, E(m)(($) over tilde nu), values are believed to be accurate to an average +/-2.5% at the peaks of 39 strong, medium, and weak bands and +/-1.9% at the peaks of 51 very weak bands below 4100 cm(-1). Above 4100 cm(-1), 11 very weak bands have an average accuracy of +/-1.3%. The baseline k(($) over tilde nu) values are accurate to between +/-3 and +/-10%. The areas under bands or band groups in k(($) over tilde nu) and epsilon(m)(($) over tilde nu) spectra are accurate to 2.4% on average, or 1.2% for strong, medium, and weak band groups between 3150 and 775 cm(-1);with 0.002 < k(max) < 0.112. The real refractive index, n(($) over tilde nu), values are believed to be accurate to 0.2%.