CO-LASER PHOTOACOUSTIC-SPECTROSCOPY ON DIMERIZATION OF FATTY-ACID MOLECULES

Absorption spectra of fatty-acid molecules with carbon number below fi ve were recorded as a function of temperature and partial pressure in the 1560-1950 cm(-1) wavelength range using photoacoustic spectroscopy with a CO laser as radiation source. A special Helmholtz PA cell prov iding good temperature uniformity and stability was developed and used to study flowing gaseous mixtures at varying temperatures. Dimerizati on enthalpies Delta H for acetic (Delta H = 60.8 +/- 3.5 kJ/mole), pro pionic (Delta H = 62.4 +/- 4.0 kJ/mole), acrylic (Delta H = 61.0 +/- 3 .5 kJ/mole) and butyric (Delta H = 58.7 +/- 1.0 kJ/mole) acid agree we ll with values obtained by other methods.