Pressure of Saturated Salt Solutions

Vapor Pressure of Fluids at Temperatures below 300 K Vapor Pressure of Saturated Salt Solutions lUPAC Recommended Data for Vapor Pressure Calibration Enthalpy of Vaporization Enthalpy of Fusion... 

Ethyl S-n-butyl xanthate. Use 32 g. of potassium ethyl xanthate, 37 g. (23 ml.) of n-butyl iodide (Section 111,40) and 50 ml. of absolute ethyl alcohol. Reflux on a water bath for 3 hours. Pour into 150 ml. of water, saturate with salt (in order to facilitate the separation of the upper layer), remove the upper xanthate layer, wash it once with 25 ml. of saturated salt solution, and dry with anhydrous calcium chloride or anhydrous calcium sulphate. Distil from a 50 ml. Claisen flask under reduced pressure. Collect the pale yellow ethyl S-n-butyl xanthate at 90-91°/4 mm. The yield is 34 g. 

The curves in Fig. 10 were drawn for the particular instance of a volatile solute dissolved in a volatile solvent, such as would exist for the acetone-chloroform system (whose diagram is very nearly like that of Fig. 10B). For many nonvolatile solutes, it not possible to trace smooth partial pressure curves across the entire range of mole fractions. This is especially true for aqueous salt solutions, where at a certain concentration of solute the solution becomes saturated. Any further addition of crystalline solute to the system does not change the mole fraction in the liquid phase, and the partial pressure of water thereafter remains constant, in accord with the phase rule. This phenomenon permits the use of saturated salt solutions as media to establish fixed relative humidity values in closed systems [12],... 

D. 3,6,9-Tris(p-tolylsulfonyl)-3,6,9-triazaundecane-l,ll-dimeth-anesulfonate (4). A 3-1., three-necked, round-bottomed flask is equipped with a mechanical stirrer, addition funnel, nitrogen inlet, and low-temperature thermometer. The flask is charged with a dried solution of 200 g. (0.306 mole) of diol 3 and 100 ml. of triethylamine in 1500 ml. of methylene chloride (Note 5). The stirred solution is held at -15 to -20° in a dry-ice-acetone bath as 50 ml. (74 g.) of methanesulfonyl chloride (Note 1) is added over 10 minutes. The dry-ice bath is replaced by an ice bath, and the solution is stirred for 30 minutes, poured into a mixture of 11. of crushed ice and 500 ml. of 10% aqueous HC1 solution, and shaken. The layers are separated, and the organic layer is washed with two 500-ml. portions of water and 500 ml. of saturated salt solution, then dried over anhydrous magnesium sulfate. The solution is filtered and evaporated to dryness under reduced pressure to give a white solid, which is dissolved in 250 ml. of methylene chloride and crystallized by addition of 500 ml. of ethyl acetate and cooling in an ice bath. The yield of methanesulfonate 4 is 215-235 g. (87-95%), m.p. 146-148°. 

Water isotherms were determined in the following way Samples of 80-100 mesh coal were evacuated at 100°C. for 2 hours in a glass tube and were then transferred to weighing bottles. The dried samples were exposed in a vacuum desiccator to water vapor from a series of saturated salt solutions with relative pressures ranging from 0.11 to 0.96 (6). The desiccator was kept in an air thermostat maintained at 35 0.5°. It was evacuated to a pressure of less than 5 mm. and then closed for equilibration. Seven days were allowed for equilibration at each sorption point. In previous work (1) this time was found to be sufficient for attaining equilibrium. 

Several methods allowing the determination of adsorption isotherms exist. The most economical one is the use of saturated salt solutions, generating known water partial pressures, followed by the measurement of the silica weight uptake. However, the time needed to obtain a suitable adsorption isotherm is excessively long (several weeks), and experimental precautions need to be taken to achieve meaningful results. Specialized equipments, quite expensive ones, have been developed for the water adsorption isotherm determination, based on highly sensitive microbalances. 

In all such methods, the solvent activity is measured over a range of solute concentrations. For example, solvent activity for a vapor-saturated aqueous salt solution can be easily determined from the decrease in vapor pressure of the salt solution relative to that of pure water, using the apparatus illustrated in Figure 17.7a. This technique... 

Membranes were dried under vacuum at 120°C and placed into closed bottles containing various water vapor pressures. Different saturated salt solutions were used to obtain the desired water vapor pressure. Solubility coefficients were obtained from the gravimetric measurement of the water sorbed into the membrane. 

TABLE 17. Salt VAPOUR PRESSURES (mm Hg) OF SATURATED AQUEOUS SOLUTIONS IN EQUILIBRIUM WITH SOLID SALTS Temperature % Humidity 10" 15" 20" 25" 30" at 20" ... 

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