Thermal investigations of the structure of two humic acid salts by in situ FTIR spectroscopy

Diffuse reflectance infrared Fourier-transformed (DRIFT) spectra of two humic sodium salts (ALDRICH, SERVA) have been recorded to study structural changes caused by heating. In situ investigations during the heating process has been accomplished by using a reaction chamber. The equilibrium of carbonate species dissolved in pore water (HCO₃^–, CO₃^2–) has been studied. Decreasing OH and C=O band intensities and the formation of CO₂ and CH₄ have been observed. An increasing absorption of the band at 2170 cm^–1 indicates changes of nitrogen linkages in the molecule. Observable amounts of nitrile groups have been formed only at temperatures around 400°C.Dedicated to Professor Dr. H. Kriegsmann on the occasion of his 70th birthday