1984 Volume 10 Issue 4 Pages 421-426
The specific heats and the differential heats of solution for NH4Br-NH3 and NH4I-NH3 systems were measured in order to construct enthalpy-concentration charts for these systems.
A twin calorimeter was used. Specific heat measurements were carried out at concentrations of ammonium bromide or ammonium iodide from 0 to 70 wt% and temperatures from 10 to 50°C. Differential heats of solution were measured over a concentration range from 0 to 70 wt% at 25°C. Integral heats of mixing were calculated from the differential heats of solution observed in this work and the differential heats of dilution estimated from the activities of these solution systems.
The accuracy of the twin calorimeter was examined by measuring the heat of solution of tris (hydroxymethyl) aminomethane (THAM) in 0.1 N HCl (aq.) and 0.1 N NaOH (aq.) at 25°C The maximum deviation from literature data was within 3%.