Vapor pressure and water activity measurements of saturated salt solutionsmade with D2O at 20 degrees C

The water activity (a(w)) values of 10 saturated salt solutions made with D 2O were measured in this study at 20 degrees C: MgCl2, K2CO3, Mg(NO3)(2), K I, NaCl, KCl, ZnSO4, BaCl2, KNO3, and K2SO4 These salts were selected becau se they represent a wide range of water activity values, from approximately 0.33 to 0.98. The a(w) values were measured using two methods: (1) a vapor pressure manometer, and (2) an electronic chilled-mirror (AquaLab) instrum ent. The a(w) values obtained by the manometer method were slightly, but co nsistently, higher than the a(w) values obtained by the electronic chilled- mirror instrument. The a(w) values of the saturated salt solutions made wit h D2O (as measured by both methods) were also slightly, but consistently, h igher than the a, values of the same saturated salt solutions made with H2O at 20 degrees C. (C) 1999 Elsevier Science Ltd. All rights reserved.