Ceramics-Silikáty 17, (4) 283 - 293 (1973)

Equilibrium in the system CaO-H₂O within the water vapour pressure range of 0.28-800 torr and temperature range of 170-524 °C was measured by the DTA apparatus using the isothermic method. The relation between log p and 1/T isothermal represents two linear sections corresponding to the equilibrium of various products. The mechanism of calcium hydroxide formation therefore has also certain variations. The reaction of calcium oxide with water vapour takes place above water vapour pressure of 82 torr and above 415 °C producing directly calcium hydroxide. At pressures below 10 torr and at temperatures below 320 °C, calcium hydroxide is formed in two stages; the first stage produces a transient product containing adsorbed or associated water [CaO H₂O] which is converted to hydroxide during the second stage.