Determination of solute properties by vapor pressure measurements of the solvent in dilute solutions

Abstract

Minor decreases in the vapor pressure of water in solution were accurately determined using a newly established method. The decreases were found to be linear with solute concentration in the range 0.02–0.1 molal. A slope for the decrease of vapor pressure for one molal solutions based on single particles was calculated and compared with the slope generally expected according to Raoult's law. The differences were found to be proportional to the charge and radius of the solute particles. An experimental rule was formulated. It provides a good fit for electrolytes, nonelectrolytes, and polyelectrolytes. The results are interpreted according to a standard state, P°i, for the vapor pressure of each solution at 10−3 molal. It is assumed that the solution obeys Raoult's law in the range 10−3−10−1 molal, substituting P°i for the vapor pressure of water. P°i is smaller than P° by about 0.2% for electrolyte and 1.5% for polyelectrolyte solutions.

A review of experimental techniques for aerosol hygroscopicity studies

“…The water vapor pressure over (or the water activity of) an aqueous solution can be determined using a number of methods (Rard and Clegg, 1997), including but not limited to (i) the static vapor pressure method, i.e., direct measurement of the vapor pressure over a solution after being degassed (Adams and Merz, 1929;Jakli and Vanhook, 1972;Apelblat, 1992); (ii) the dynamic vapor pressure method, i.e., measurements of the amount of water vapor from an aqueous solution required to saturate a given volume of air (Bechtold and Newton, 1940); (iii) measurements of the boiling temperature of an aqueous solution; (iv) measurements of the dew point or RH of the air over an aqueous solution (Hepburn, 1932); and (v) the vapor pressure osmometry (Amdur, 1974;Sadeghi and Shahebrahimi, 2011). These techniques are described elsewhere (Pitzer, 1991;Rard and Clegg, 1997), and interested readers are referred to the two papers (and references therein) for more information.…”

A review of experimental techniques for aerosol hygroscopicity studies

“…direct measurement of the vapor pressure over a solution after being degassed (Adams and Merz, 1929;Jakli and Vanhook, 1972;Apelblat, 1992); (ii) the dynamic vapor pressure method, i.e. measurements of the amount of water vapor from an aqueous solution required to saturate a given volume of air (Bechtold and Newton, 1940); (iii) measurements of the boiling temperature of an aqueous solution; (iv) measurements of the dew point or RH of the air over an aqueous solution (Hepburn, 1932); and (v) the vapor pressure osmometry (Amdur, 1974;Sadeghi and Shahebrahimi, 2011). These techniques are described elsewhere (Pitzer, 1991;Rard and Clegg, 1997), and interested readers are referred to the two papers (and references therein) for more information.…”

A review of the osmotic coefficients of aqueous calcium chloride at 25.degree.C

“…Consider an electrolyte solution of molality m, with a water activity a 1 and each molecule of electrolyte dissociating into v ions. The osmotic coefficient of this solution is given by 1000 In a1 vmMi (1) where M1 = 18.0154 g mol-1 is the molecular weight of water. If this solution is in isopiestic equilibrium with a standard solution, = ' * m* vm (2) where the asterisk refers to the standard solution.…”