The development of low temperature heat capacity results : a heat capacity study of some chloroammine cobalt(III) compounds

Abstract

A laboratory for heat capacity measurements by adiabatic calorimetry in the range from 2 to 100 kelvin was developed. A complete vacuum and gas-handling system was designed and constructed to serve a refurbished pumped-helium cryostat. Automatic data-collection, real-time display of temperature and semi-automation of heating and adiabatic control were achieved with a low-cost interface and microcomputer. The apparatus was calibrated with a benzoic acid thermometric standard. The heat capacity of chloropentaammine cobalt(III) dichloride was measured from 3.8 to 100 kelvin; thermodynamic functions are quoted from 6 to 100 kelvin. The heat capacity of trans-dichloro-tetrammine cobaltdil) chloride was measured from 4.7 to 100 kelvin; thermodynamic functions are quoted from 10 to 100 kelvin. No thermal anomalies were observed in these temperature ranges.