Gas solubility Ostwald coefficient

The Ostwald solubility coefficient j3, i.e. the ratio of the concentration of the dissolved substance in the solution phase to the concentration of the dissolved substance in the gas phase is, at 297.5 K, 0.201. In the pressure range of 100 to 700 mmHg it is independent of pressure so that, at least below 1 atm, Henry s law is obeyed. With increasing temperature / decreases and reaches a value of 0.137 at 323.2 K. The enthalpy of solution calculated from the temperature dependence of P is -2.95 0.1 kcal/mol 9. 

The inhalational anesthetics have distinctly different solubility (affinity) characteristics in blood as well as in other tissues. These solubility differences are usually expressed as coefficients and indicate the number of volumes of a particular agent distributed in one phase, as compared with another, when the partial pressure is at equilibrium (Table 25.3). For example, isoflurane has a blood-to-gas partition coefficient (often referred to as the Ostwald solubility coefficient) of approximately 1.4. Thus, when the partial pressure has reached equilibrium, blood will contain 1.4 times as much isoflurane as an equal volume of alveolar air. The volume of the various anesthetics required to saturate blood is similar to that needed to saturate other body tissues (Table 25.3) that is, the blood-tissue partition coefficient is usually not more than 4 (that of adipose tissue is higher). 

The Ostwald solubility coefficient L is the gas-liquid partition coefficient defined as ... 

In anaesthetic practice, an alternative solubility coefficient, the Ostwald solubility coefficient, is preferred. This coefficient is defined as the volume of gas which dissolves in a unit volume of the liquid at the given temperature. The volume of gas is not corrected to standard temperature and pressure but instead is measured at the temperature and pressure concerned. The important difference between these two coefficients is that the Ostwald coefficient is independent of pressure, as we can see from the following example. 

Ostwald solubility coefficient. The graph shows that an anaesthetic gas with a high oil solubility is effective at a low alveolar concentration and has a high potency. This relationship is the basis of the Meyer-Overton hypothesis of anaesthesia. 

The solubility of a gas in a liquid may be expressed by the Ostwald solubility coefficient, which is the volume of gas dissolved in unit volume of liquid at a given temperature, or as the Bunsen s absorption coefficient, in which the temperature and pressure are reduced to standard conditions. The solubility of a gas in a liquid decreases with increase of temperature at constant pressure and is directly proportional to pressure at a constant temperature (Henry s law). 

The only tricky thing about Bunson and Ostwald solubility coefficients is that they represent a volume of gas per volume of solvent (not solution). Because gases increase the volume of the solution when they dissolve into it, a correction has to be made for this difference. The correction is significant and on the order of 0.14% (Weiss, 1971). The values presented in Table 3.6 have not been corrected for this effect, and since this is a potential point of confusion, we will use the Henry s Law coefficient most often in this book. 

Gas-solvent partition coefficient is known as the Ostwald solubility coefficient L and is usually written in the logarithmic form as [Katritzky, Mu et al., 1996a Katritzky,... 

Additional experimental data of direct relevance to this chapter are the many thermodynamic measurements of gas solubiHty. An extensive set of experimental measmements below water s normal boiling point have been compiled and reviewed by Wilhelm, Battino, and Wilcock. Solubility data at higher temperatures are available from a more recent article by Fernandez Prini and Crovetto. Gas solubilities are often tabulated in terms of the Ostwald solubility coefficient... 

The volume in milliliters of gas dissolved per milliliter of liquid at one atmosphere of partial pressure of the gas at any given temperature. Thus, the Ostwald coefficient (A) differs from the Bunsen solubility coefficient (a) which is based on standard temperature and pressure. The two coefficients are related by the equation A = a(l + 0.00367t) where t is the temperature in degrees Celsius. 

The solubility was expressed in terms of the Ostwald absorption coefficient, L, which is defined as the ratio of the volume of absorbed gas to the volume of absorbing liquid at the temperature and pressure of the measurement. This is because the Ostwald coefficient is really an equilibrium constant, and the method of correction to standard conditions does not need to be specified in comparison with the Bunsen coefficient. 

The Ostwald partition coefficient, L, is a widely used and physically intuitive measure of gas solubilities and oil-water partition coefficients. It is defined as the ratio of concentrations of a solute between two phases at equilibrium. These two phases can be the ideal gas and a liquid phase, in which case the Ostwald partition coefficient gives the gas solubility, or two immiscible liquids - e.g., oil and water - in which case L is an oil-water partition coefficient. For the gas solubility of component 2 in liquid 1,... 

The solubility of common gases in hydrocarbon liquids is determined to meet requirements of aerospace industry. This test method is based on the Clausius-Clapeyron equation, Henry s law, and the perfect gas law. The results are important in the lubrication of gas compressors where dissolved gas may cause erosion due to cavitation. In fuels, dissolved gases may cause interruption of fuel supply and foaming in tank. The liquid density is determined experimentally. Using this density, the Ostwald coefficient is taken from a chart and used for e calculation of the Bunsen coefficient (solubility of gas). The solubility of the gas or mixture of gases and Henry s law constant are also calculated. 

At any partial pressure of gas, p, , the mole fraction solubility may be calculated from Ostwald s coefficient L as. 

The solubility of a gas will always be given in terms of the Ostwald absorption coefficient. This is defined as follows Let be the volume of the gas (at a given T and P) dissolved in a given volume of liquid (at the same T and P). The Ostwald absorption coefficient is defined by... 

For historical reasons, there are several different ways to express gas solubilities in liquids, such as Bunsen s and Ostwald s coefficients. These are not treated here in detail, and the reader is referred to Refs. [1] and [2]. Nowadays, the most common means to express gas solubilities is to turn to the equilibrium molar fractions or x) of dissolved gas A and to the temperature and pressure of the gas. From the ratio... 

The solubilities of gases in liquids may be expressed in various ways. In the definition of the Bunsen coefficient the solubility is expressed as the volume of the ideal gas reduced to O C and 1 atm pressure soluble in a unit volume of liquid under the gas pressure of 1 atm and at the temperature of measurement. The Ostwald solubility ki — Vgl V oiy is defined as the ratio of the volume of absorbed gas to the volume of the absorbing liquid, measured at the same temperature. The Bunsen solubility coefficient a and the Ostwald coefficient L on the assumption of ideal gas behavior are related to the simple g-moles/liter concentration scale c by the relationships which are applicable when P = 1 atm ... 

Ostwald coefficient physchem A measure of the solubility of a gas in a liquid, equal to the volume of gas that can be dissolved in a given volume of liquid divided by the volume of liquid. ast.valt, ko-3,fish-ant ... 

Gas solubilities may be expressed as (1) volume of gas dissolved in unit volume of solvent, known as the Ostwald coefficient, designated by r ... 

Kamlet-Taft) electron pair donation ability Ostwald coefficient (for gas solubility) mean ionic activity coefficient... 

The solubility of gases is generally described by the Ostwald coefficient L = Vs/Tw, where subscripts s and w denote the solute and the solvent (water), and Vs denotes the volume of pure gas at a given temperature and pressure sorbed by (dissolved in) a volume Vw of pure water. For the standard pressure of =0.1 MPa 1 atm (the Ostwald coefficient is not appreciably dependent on the pressure at moderate pressures) the standard state molar volume of the gas is Vs° =RT/P° + Bss, the second term is the second virial coefficient of the gas (describing interactions of the gas molecules with each other) and generally Bss RT/P° and can be ignored. The molar concentration (in Vw = 1 dm of water) of the gas is then LP°IRT (with... 

This work, on the other hand, is empirically related to the Ostwald coefficient Lsw for the solubility of the organic liquid as a gaseous solute in water, Lsw = cs-in-w/cs-gas. 

Another factor of interest for studies in this area is the solubility of the gas in the liquid phase. This is needed to calculate the mass transfer rate and the molar concentration at saturation of the gas at a particular partial pressure of the gas. However, gas solubilities are rarely given in molar units. Most commonly, one finds the Ostwald coefficient, L, which is the concentration in the liquid phase divided by the concentration in the gas phase (i.e. the equilibrium constant for G(g) to G(o), or the Henry s law constant, H, which usually is defined as the partial pressure of the gas, P(g>,... 

Table 10 Solubility of Gases in Liquid Hydrocarbons at 25°C and a Gas Pressure of 1.013 bar L, Ostwald Coefficient X, Mole Fraction Solubility...

For the comparison of solubilities on a molecular basis, it is invalid to use either the Ostwald or the Bunsen coefficient this is because the density and molecular weight of the liquid S are always material factors, and the deviation of the gas A from ideality can also be a material factor. Markham and Kobe showed that in the example of carbon dioxide, the assumption of the ideal gas laws could make a... 

Lannung (1930) gave solubility results for He, Ne, and Ar in water, methanol, ethanol, acetone, benzene, cyclohexane, and cyclohexanol for different temperatures from 5 to 45 C. He gave his results as the Bunsen absorption coefficient a. He gave the Ostwald coefficient L, where L = aT/273 and T is the r K of the measurement, but he defined L as the equilibrium ratio of the volume concentrations of the gas in the solution and in the vapor phase. ... 

Bearing in mind that the Henry s law constant was given as (vol. CO2/V0I. solution)/PCO2 the summary given in the abstract indicates that at low temperatures Henry s law was more nearly followed when the volume of gas was related to the volume of the solution rather than to the volume of the solvent. In Fig. 1551 have compared the vol. CO2/V0I. solution plot with that for vol. CO2/V0I. S for propanol and benzene at different pcoj and at 20°C. To convert vol. A/vol. S (Ostwald coefficient) data into Xa data, the density and molecular weight of the original liquid S are material factors. The statement that the solubility (vol./vol.) decreases with the increase in molecular weight of S, even if the liquids S are chemically related, is, on a molecular basis, invalid. See Table 45. 

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