NITRO DERIVATIVES OF TOLUENE 299THERMOCHEMICAL PROPERTIESSpecific heat. C. A. Taylor and Rinkenbach [40] give the following values
for α− trinitrotoluene at temperatures, ranging from 0°C to the melting point of the
compound :
Temperature, °C Specific heat, Cal/g °C0 0.309
20 0.328
40 0.345
60 0.361
80 0.374The thermal conductivity, λ, of α− trinitrotoluene is 0.00043 at 25° (Prentiss [73]).
Heat of crystallization and heat of evaporation. According to Tammann [74],
the heat of crystallization of α− trinitrotoluene is 4.88 Cal/mole, and according
to Edwards [69] is 5.6 Cal/mole. The heat of evaporation of α− trinitrotoluene,
as found by Edwards [69], equals 22.7 Cal/mole. According to A. J. B. Robertson
[66], it is 17.5 Cal/mole.
Heat of combustion and heat of formation. The heat of combustion of α− trini-
trotoluene is 822.5 Cal/mole (Garner and Abernethy [3]). The value relates to con-
stant volume and includes a correction that allows for the nitric acid formed in the
calorimetric bomb.
From the measured heat of combustion, the heat of formation of α− trinitroto-
luene has been calculated as +29.1 kcal/mole (assuming amorphous carbon), or
+128.2 kcal/kg. Assuming the diamond form for carbon, Abemethy and Gamer
[3] found a lower heat of formation, viz. +10.2 kcal/mole (Fig. 50. p. 261).
Other authors give the following values for the heat of formation of α− trinitro-toluene :
+ 16.0 kcal/mole (Kast [54])
+ 7.7 kcal/mole (Bichel [22])
+ 5.9 kcal/mole (Koehler [23])For calculating the thermal effects of the processes in which α− trinitrotoluene
takes part the values given by Gamer and Abernethy, or by Kast are generally
used.
Heat of nitration. The heat of conversion of dinitrotoluene to trinitrotoluene,
calculated from the heats of formation of the reactants and of the reaction products
is:+ 17.5 kcal/mole (starting product 1,2,4-dinitrotoluene) (Fig. 50)
+ 19.0 kcal/mole (starting product 1,2,6-dinitrotoluene)Heat of explosion is discussed later (under explosive properties p. 318).