Vacuum-jacketed hydrofluoric acid solution calorimeter

A vacuum‐jacketed metal calorimeter for determining heats of solution in aqueous HF was constructed. The reaction vessel was made of copper and was heavily gold plated. The calorimeter has a cooling constant of 0.6 cal‐deg⁻¹‐min⁻¹, approximately ¼ that of the air‐jacketed calorimeters most commonly used with HF. It reaches equilibrium within 10 min after turning off the heater current. Measurements of the heat of solution of reagent grade KCl(−100 mesh dried 2 h at 200°C) at a mole ratio of 1 KCl to 200 H₂O gave ΔH = 4198±11 cal at 25°C.