Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

In the present work temperature dependence of heat capacity of l-carnitine has been measured for the first time over the range from 6 K to 346 K by precision adiabatic vacuum calorimetry. Based on the experimental data, the thermodynamic functions of the l-carnitine, namely, the heat capacity , enthalpy Hdeg.(T) - Hdeg.(0), entropy Sdeg.(T) - Sdeg.(0) and Gibbs function Gdeg.(T) - Hdeg.(0) have been determined for the range from T -greater than 0 to 350 K. The value of the fractal dimension D in the function of multifractal generalization of Debye's theory of the heat capacity of solids was estimated and the character of heterodynamics of structure was detected. Enthalpy of combustion (-4142.1 +- 2.3) kJ mol-1 of the l-carnitine was measured for the first time using high-precision combustion calorimeter. The standard molar enthalpy of formation in the crystalline state (-756.2 +- 2.5) kJ mol-1 of l-carnitine at 298.15 K was derived from the combustion experiments. Using combination of the adiabatic and combustion calorimetry results the thermodynamic functions of formation of the l-carnitine at T = 298.15 K and p = 0.1 MPa have been calculated. The low-temperature X-ray diffraction was used for the determination of coefficients of thermal expansion.