Abstract
The effects of sample mass and particle size on the determination of kinetic parameters with the calculation procedures of Ozawa and Kissinger in differential scanning calorimetry were studied with factorial designs. Sodium bicarbonate, three organic hydrates (potassium oxalate hydrate, mercaptopurine hydrate, and sodium citrate dihydrate) and two substances giving solid-solid transformations (potassium nitrate and hexamethylbenzene) were studied. It was found that both sample mass and particle size could influence the values of the kinetic parameters, but the extent of these effects was different for each substance. The Kissinger procedure did not have practical advantages over the Ozawa method. In some cases it was necessary to use the temperature at half conversion instead of peak temperatures in the Ozawa plotting, because the conversions at peak temperature could vary considerably with heating rates. Sharp and narrow transition peaks were found to lead to extremely high values of activation energy and pre-exponential factor. It is not justified to attribute any physical meaning to such values.
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