Calculating the critical relative humidity from the solubility of electrolyte according to extended non-random two liquid model.

According to thermodynamic principle, the critical relative humidity of electrolytes is closely related to their solubility. The authors explored the relationship theoretically and calculated the critical relative humidity of 21 electrolytes in the light of Raoult's law, modified Debye-Hückel model and extended non-random two liquid (NRTL) model from their solubility. The results indicate that the critical relative humidity values calculated by Raoult's law can not accord with the reported ones and there is a systematic error in high concentration range; the values calculated by modified Debye-Hückel model still can not accord with the reported ones well although without systematic error; and the values calculated by extended NRTL are comparable to the reported ones.