The Effect of Pressure and Temperature on the Absorption Spectrum of Benzene in the Near Ultraviolet

The absorption spectrum of benzene vapor in the near ultraviolet was photographed at temperatures varying from room temperature up to above the critical temperature (287°C), and at the corresponding pressures of the saturated vapor (from a few mm of mercury up to about 50 atmos). Changes of the intensity distribution within each of the groups of bands were found, which gave a shift in the maxima of these groups, but even at the highest temperatures and pressures near the critical point, no measurable shift in the frequencies of the components of the groups was found. This shows that the effect of intermolecular forces on the frequencies of the bands is very small. A short discussion of the results is also given.