The osmotic pressure of ammonium sulfate solutions has been measured by the well-established freezing point osmometry in dilute solutions and we recently reported air humidity osmometry in a much wider range of concentration. Air humidity osmometry cross-validated the theoretical calculations of osmotic pressure based on the Pitzer model at high concentrations by two one-sided test (TOST) of equivalence with multiple testing corrections, where no other experimental method could serve as a reference for comparison. Although more strict equivalence criteria were established between the measurements of freezing point osmometry and the calculations based on the Pitzer model at low concentration, air humidity osmometry is the only currently available osmometry applicable to high concentration, serves as an economic addition to standard osmometry.

Based on thermodynamic principle, the critical relative humidity of electrolytes is closely related to their solubility. The authors explored the relationship theoretically and calculated critical relative humidity of 21 electrolytes from their solubility in the light of Raoult's law and extended Wilson model. 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 the high concentration range; while these calculated by extended Wilson model are comparable to the reported ones.

Objective　This experiment was designed to make known wether the photostability of drugs in daylight can be obtained from lamplight exposure. Methods　A self made cumulative illuminometer via pulse counting method was used for measuring cumulative illuminance of daylight to investige the photodegradation of Hydrocortisone injection in various lamp light and daylight; the equivalent influences of different light sources on the photostability of the injection were obtained，and the shelf-life in indoor daylight of the drug was predicted. Results　The photodegradation of Hydrocortisone injection obeys zero order kinetics: C=C0-kEt; the shelf-life in indoor daylight of the injection in nude ampoules was predicted as 36 days and is comparable to 35 days in a long-term storage test. Conclusion　The photostability of drugs in daylight can be obtained from lamplight exposure experiment.