Thermal decomposition of some chemical compounds used as food preservatives and kinetic parameters of this process

Thermal decomposition processes of selected chemicals used as food preservatives such as sodium formate, sodium propionate, sodium nitrates(V and III) and sodium sulphate(IV) were examined by the derivatographic method. Based on the curves obtained, the number of decomposition stages and characteristic temperatures of these compounds have been found. Mass decrements calculated from TG curves ranged from 28.9% for sodium formate to 77.8% for sodium nitrate(V), while sodium sulphate showed a mass increment of 5.6%. Kinetic parameters such as activation energy (E-a), frequency factor (A) and reaction order (n) were calculated from TG, DTG and T curves. Sodium formate shows the highest values of E-a and A which amount to 171.7 kJ mol(-1) and 5.8.10(14) s(-1), respectively, while the lowest ones, E-a=28.2 kJ mol(-)1 and A=3.65.10(2) s(-1) belong to sodium nitrate(V).