The use of thermogravimetry to follow the rate of evaporation of an ingredient used in perfumes

Ingredients used in the manufacture of perfumes can be investigated by thermogravimetry. In this study the evaporation of methyl benzoate was investigated using a simultaneous TG-DTA unit. A rising temperature method of thermal analysis was used for the study. The rate of evaporation of the ingredient was calculated from a simple plot of percentage mass loss vs. time. A derivative plot of the same was used to calculate the coefficient of evaporation in a controlled atmosphere and regulated air flow rate. In a series of programmed temperature runs on the TG-DTA unit it was shown that the evaporation process is zero order, and that the evaporation coefficients at each temperature can be fitted into the Arrhenius equation. The energy of activation, E-act can be calculated from the slope of the line. It was found to be 47 kJ mol(-1). This value was compared and shown to approach the enthalpy of vaporization as calculated using the Troutons or Clausius Clapeyron equation.