The industrial production of poly (ethylene terephthalate), PET, continues to increase and thus it is important to understand the composition of fumes resulting from its disposal as a part of incinerated waste. In this study samples of PET material were combusted in a furnace corresponding to the German standard DIN 53,436 at temperatures of 500°C, 800°C (in an air flow) and also uncontrolled combustion in air. The gaseous products were then analysed using three different analytical methods: high resolution Fourier transform infrared spectroscopy (FTIR), selected ion flow tube mass spectrometry (SIFT-MS) and gas chromatography mass spectrometry (GC-MS). Carbon dioxide, methane, ethylene, acetylene, formaldehyde (methanal) and acetaldehyde (ethanal) were detected by FTIR. Water, methane, acetaldehyde, ethylene, formaldehyde, methanol, acetone, benzene, terephthalic acid, styrene (ethenylbenzene), ethanol, toluene (methylbenzene), xylene (dimethylbenzene), ethylbenzene, naphthalene, biphenyl and phenol concentrations were all quantified by both SIFT-MS and GC-MS. Additionally, the fumes resulting from uncontrolled combustion in air were analysed by FTIR which resolves the rotation–vibration structure of the absorption bands of formaldehyde (2779.90 and 2778.48 cm⁻¹) and propane, which was identified from characteristic vibrations of CH₃ groups at 2977.00 and 2962.00 cm⁻¹. The spectra were compared with reference standards.

Seven inorganic salts of 3,5-diamino-1,2,4-triazole (dat) with inorganic acids were prepared within our project focused on the crystal engineering of novel NLO materials and their X-ray structures were determined. Three triclinic compounds, dat(1+) selenate dihydrate, dat(1+) sulphate dihydrate and dat(1+) perchlorate, crystallize in the space group P. Three monoclinic structures of dat(1+) – i.e. nitrate, chloride hemihydrate and hydrogen phosphite crystallize in P2₁/c, P2₁/n and P2₁/c, respectively. Finally, the most promising structure of dat(1+) dihydrogen phosphate is orthorhombic (the space group Fdd2). The structure is formed by anionic layers parallel to the ac plane and the cationic chains parallel to the c axis. The FTIR and Raman spectra of the title compounds have been recorded and discussed. The assignment of the spectra is based on a quantum-chemical calculation and the factor group analysis. Quantitative powder measurements of the second harmonic generation of the only non-centrosymmetric dat(1+) dihydrogen phosphate at 1064 nm were performed and a relative efficiency equal to KDP (i.e. potassium dihydrogen phosphate) was observed. The consequent study of single crystal samples enabled the estimation of NLO tensor coefficients of this material.