Thermal expansion of α-trinitrotoluene from 77 to 273 K

Abstract

Relative length changes in orthorhombic crystals of α-TNT have been measured from 77 to 273 K. Using a three-terminal capacitance technique, length changes were measured with a resolution of 10−9 cm under optimum conditions. Relative temperature changes of 1 part in 105 were detected with a platinum resistance thermometer used as one arm of an ac resistance bridge. The linear expansion coefficient calculated from these data is found to have a second-order transition with a critical temperature, Tc = 211.7 K. Mangelsdorf plots indicate logarithmic behavior of the linear expansion coefficient along all crystalline axes for the temperature intervals 203 K < T < Tc and 223 K < T < Tc. The volume expansion coefficient was obtained from the three linear expansion coefficients.