The enthalpy of fusion for gallic acid (or 3,4,5-trihydroxybenzoic acid) was estimated as 30.96 kJ/mol [1] using the group contribution method proposed by Joback and Reid [2].
It should be kept in mind that gallic exhibits a significant vapor pressure near its melting point. That is, the enthalpy of fussion depends on whether the melting occurs in an open or closed system. In open (isobaric) system, the gallic acid melts and evaporates/sublimes simulataneously and the corresponding enthalpy change is higher than in the case of closed system, where evaporation/sublimation is suppressed.