Pressure of solutions

The osmotic pressure of solutions of polystyrene in cyclohexane was measuredf at several different temperatures, and the following results were obtained ... 

Temperature, °C Urea ia solution, wt % Vapor pressure of solution, kPa... 

In order to define completely the solubility of a gas in a liquid, it generally is necessary to state the temperature, the equilibrium partial pressure of the solute gas in the gas phase, and the concentration of the solute gas in the liquid phase. Stric tly speaking, the total pressure on the system also should be stated, but for low total pressures, less than about 507 kPa (5 atm), the solubihty for a particular partial pressure of solute gas normally will be relatively independent of the total pressure of the system. 

The vapour pressure of the solution at the freezing-point is equal to that of pure ice at the same temperature (Guldberg, 1870). For if we take the system ice, solution, vapour, at the freezing-point, and suppose that p p" are the vapour pressures of solution and ice, , v" the specific volumes of the vapour under these pressures, and V, V" the specific volumes of solution and ice, we may execute the following isothermal cycle ... 

The isopiestic method was first introduced by W. R. Bousfield. "Isopiestic Solutions." Trans. Faraday Soc., 13, 401-410 (1918) and refined by D. A. Sinclair. A Simple Method for Accurate Determinations of Vapor Pressure of Solutions". J. Plus. Chem., 37.495-504 (1933). 

Numerous measurements of the conductivity of aqueous solutions performed by the school of Friedrich Kohhansch (1840-1910) and the investigations of Jacobns van t Hoff (1852-1911 Nobel prize, 1901) on the osmotic pressure of solutions led the young Swedish physicist Svante August Arrhenius (1859-1927 Nobel prize, 1903) to establish in 1884 in his thesis the main ideas of his famous theory of electrolytic dissociation of acids, alkalis, and salts in solutions. Despite the sceptitism of some chemists, this theory was generally accepted toward the end of the centnry. 

Understand the clinical significance of the osmotic pressures of solutions... 

In case of solutions of high Molecular weight compounds, the selection of semi-permeable membrane is easier, because the solvent and the solute molecules are quite different in their size. The relationship between the Osmotic pressure of solution of a macromolecular compound and the Molecular weight is widely used for determination of Molecular weights and in the study of the interaction between the solvent and the solute molecules in the solution. 

Roughly half of the data on the activities of electrolytes in aqueous solutions and most of the data for nonelectrolytes, have been obtained by isopiestic technique. It has two main disadvantages. A great deal of skill and time is needed to obtain reliable data in this way. It is impractical to measure vapor pressures of solutions much below one molal by the isopiestic technique because of the length of time required to reach equilibrium. This is generally sufficient to permit the calculation of activity coefficients of nonelectrolytes, but the calculation for electrolytes requires data at lower concentrations, which must be obtained by other means. 

Partial pressure of solute in gas phase (kN/m2) Concentration of solute in water kg/1000 kg water ... 

His works are known in studies on osmotic pressures and vapor pressures of solutions, but he is much better known as the discoverer of glutamic acid extracted from sea tangle (Konbu, a seaweed, in Japanese) and the producer of the seasoning Aji-no-Moto (sodium glutamate). His wife, Sada, is a younger sister of the wife of Joji Sakurai. 

Figure 7.4 Representations of hydrodynamic flow, showing (a) laminar flow through a smooth pipe and (b) turbulent flow, e.g. as caused by an obstruction to movement in the pipe. The length of each arrow represents the velocity of the increment of solution. Notice in (a) how the flow front is curved (known as Poiseuille flow ), and in (b) how a solution can have both laminar and turbulent portions, with the greater pressure of solution flow adjacent to the obstruction.

Figure 17.1. Partial pressure of solute as function of molality p 2 represents the vapor pressure along the broken line) (Henry s law).

Figure 17.2. Determination of partial pressure of solute in its standard state.

Fenclova and Dohnal [11] have measured the liquid and vapor compositions and total pressures of solutions of 1,1,2-trichlorotrifluoroethane (Freon) [1] and n-hexane[2] at 308.15 K. Their results are given in Table 17.6. 

Wahid, H. Light scattering from binary liquid systems. II. The partial pressure of solutions. Phys. Chem. Liq., 26 171-177, 1993. 

This is a form of Henry s law, where the Henry s law constant is simply the product of the vapor pressure of solute 2 multiplied by the energy correction term exp(Ae/ 7 ). For oleophilic substances, which do not like water, mixing is an endothermic process and the term Ae/kT is positive, so that Henry s law constant is much higher than the vapor pressure of the pure substance. 

Figure 5.16 Partial pressure of solution, Raoult s law solution, and regular solutions with a range of values for A /RT...

Vapor Pressure Vapor pressure of solution with nonvolatile solute is lower than that of solvent... 

Biltz 4 carried out a series of investigations on the vapour pressures of solutions of silver chloride and ammonia, and came to the conclusion that silver chloride forms the triammine, [Ag(NH3)3]Cl, at atmospheric pressure below 20° ., and the sesquiammine, 2AgCl(NH3)3, at temperatures between 20° and 60° C. Above 00° C. silver chloride does not unite with ammonia. 

The osmotic pressure of solutions of a fractionated, atactic poly(isopropylacrylate) solution was measured at 25°C with the following results ... 

When the feed concentration is as small as those considered in this study, the osmotic pressure of solutions is negligible. Therefore, PR/PWP may be expected to be nearly equal to unity. However, for cases V and VI, in which strong attractive forces work between membrane and solute, PR/PWP... 

According to (7.65), the vapor-pressure lowering AP = PA — P is directly proportional to xB. As shown in the diagram, the dashed vapor-pressure curve for solution therefore falls below the solid pure-solvent curve, corresponding to the well-known effect of a nonvolatile solute in reducing the vapor pressure of solution. 

The vapour pressure of solutions of nitroglycol in nitroglycerine has been reported on p. 44 (Table 13). 

Data collected with membranes of this type played an important part in the formulation of present-day solution theory—so much so that the authors have used this theory without hesitation to compute osmotic pressures of solutions whose osmotic pressures have never been precisely measured. Such a solution is sea water. The copper ferrocyanide membrane is leaky to solutions of strong electrolytes. Some data have been obtained on weak solutions of strong electrolytes by the Townend method (16), but no one has made precise measurements on the osmotic pressure of sea water. 

AP = (vapor pressure of pure solvent) - (vapor pressure of solution)... 

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