Water-vapor pressure and thermodynamics of the dehydration of manganese, nickel, cadmium, and lead perchlorate hydrates

Abstract

The water-vapor pressure has been measured by a static method, the temperature limits for existence have been determined, and the parameters of the equation lgp [Torr]=b —a/T have been calculated for the following crystal hydrates: Mn(ClO4)2 · 2H2O (90–130°C, a=3527.0,b=8.487), Ni(ClO4)2 · 4H2O (60–100°C,a=3606.7,b=9.704), Ni(C1O4)2 · 2H2O (110–160°C,a = 4261.7,b = 10.103), Cd(ClO4)2 · 6H2O (25–58.2°C,a = 3143.7,b = 9.356), Cd(ClO4)2 · 2H2O (90–144.8°C,a=3823.3,b = 9.472), Pb(ClO4)2 · 3H2O (10–47°C,a = 2932.9,b = 9.391 and 47–81.5°C,a = 2448.1,b=7.877), Pb(ClO4)2 · H2O (60–102.4°C,a=3610.2,b = 9.857). A hitherto unknown metastable hydrate Cd(ClO4)2 · 4H2O with a phase transition at 30.9°C (20–30.9°C,a = 3669.5,b = 11.343 and 30.9–63.7°C,a=3058.6,b = 9.339) has been detected.