A method for studying the volatilisation rate of materials using a con
ventional thermobalance and standard sample holders is described. This
was used to study two dyes; CI Disperse Yellow 54 and CI Disperse Red
60. Using pure reference materials, a relationship between volatilisa
tion rate and vapour pressure based on the Langmuir equation for free
evaporation was used to calibrate the system. Thus, the vapour pressur
es of the dyes could be determined. Heats of sublimation and vaporisat
ion were calculated from a plot of the logarithm of the vapour pressur
e against reciprocal absolute temperature. Extrapolation of the vapour
pressure vs. temperature curve outside the experimentally measured re
gion for Red 60 was made using the melting point and heat of fusion fo
und by DSC. Good agreement was found with literature data. In favourab
le cases, the melting temperature and heat of fusion can be obtained d
irectly from thermogravimetry. (C) 1998 Elsevier Science B.V.