The
construction and calibration of a semi-micro-combustion calorimeter
for samples of around 35 mg is presented. The calorimeter energy equivalent
was determined using benzoic acid as the primary standard, obtaining
εcal = (2,338.81 ± 0.22) J·K–1. The operation of the calorimeter was verified by the combustion
of 1,2,4-triazole and nicotinic acid as secondary and tertiary standards,
respectively, obtaining results similar to data reported in the literature.
The calorimeter was used to determine the massic standard energy of
combustion of N,N′-bis(salicylidene)ethylenediamine
and N,N′-bis(salicylidene)-1,3-propanediamine.
In addition to the enthalpies of combustion, the molar standard enthalpies
of formation in the crystalline phase were calculated from experimental
data. Molar enthalpy of vaporization was determined by thermogravimetry
and then used to obtain the molar standard enthalpies of formation
in the gas phase. The melting temperatures and enthalpies of fusion
of these compounds were also determined by differential scanning calorimetry.