Bunsen s absorption coefficient

A. Solubility of Gases.1—This is usually expressed m one of two ways, namely, as Bunsen s Absorption Coefficient, ft, or as Ostwald s Solubility expression, l. These terms have already been defined (p. 36). 

Solubility.—Phosphine dissolves in 5 to 10 times its volume of water at ordinary temperatures. The solubility, expressed as Bunsen s absorption coefficient, is 0-26 volume at N.T.P. in 1 volume of water at 17° C.1... 

The amount of gas which can he dissolved by a particular liquid depends on the temperature, the pressure and the nature of both the gas and the liquid solvent. The solubility may be expressed by Bunsen s absorption coefficient, a, which is the volume of gas reduced to 273 K and a pressure of 1 bar which dissolves in a unit volume of the liquid at the given temperature when the partial pressure of the gas is 1 bar. 

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). 

As seen later, taking into account the hydrolysis constant of H2CP3, the percentage of carbonic acid is very small ( 0.3 %), so that Hap H is valid within the measurement errors. Fig. 2.94 shows the temperature dependency of the Bunsen s absorption coefficient a (data from D Ans and Lax 1943). This coefficient is directly related to the Henry constant via a = H - RT R gas constant), where H has the dimension mol atm h An empirical fit results in (r = 0.999), but is slightly different for two ranges of temperature ... 

The Henry coefficient He j depends on both the nature of the absorptive i and the absorbent / (washing agent). The values of the Hemy coefficients significantly increase with rising temperatures. In practice, the Bunsen s absorption coefficients a are very often used. Their definition is... 

Selected values of Bunsen s absorption coefficient a are plotted vs. temperature in Fig. 5.3-3. Often used is also the technical absorption coefficient. Here, the amount of dissolved gases is referred to the mass of pure solvents. 

Bunsen s absorption coefficient. The volume of gas (reduced to standard temperature and pressure, 0 °C and 760 Torr) absorbed by a unit volume of the solvent (water) at the indicated temperature if the partial pressure of the gas is 760 Torr. aqueous solution at a concentration of 1 mol dissolved substance per liter solution (mol 1 ). Example fi° aq (-266.66) is the heat of solution for Li2C03 in kcal. technical atmosphere (kp-cm )... 

Nonpolar components (water -subsurface gas -nonpolar liquids - organic matter of rocks) Absorption, evapouration, condensation SolubUity-C, . Saturation pressure -P. Saturated vapour pressure Solubility coefficients Henry - H., Bunsen -B.. Sechenov -S. t Coefficients of absorption distribution between water and gas-Ki, nonpolar liquid - Ki, organic m er -Kw,i, organic carbon, octanol - C , rock -Ki,i and Kw.i ... 

The temperature dependency is described by the van t Hoff equation (4.94) where the reaction enthalpy must be replaced by the enthalpy of solution A oiH. The derivation of (4.209) follows from the equality of the chemical potentials in the gas and aqueous phases in equilibrium, q ig) + RTlnPa = q (aq) + i Tln [A] from which [A] = Pa constant follows. In close relation to the Henry s law constant are the Bunsen absorption coefficient a (the volume of gas absorbed by one volume... 

Johan Fridrik Bahr (1815-1875) studied at the Uppsala university, and then worked in Bunsen s laboratory in Heidelberg. In their cited paper they introduced the concept of extinction coefficient so important in absorption photometry. Later Bahr worked as first assistant at the Uppsala university. 

As well as Henry s constant // , a measure of the capacity of a liquid to dissolve a gas, are the Bunsen absorption coefficient Obu, and the Oswald absorption coefficient Oqsj, which can be found in tables. The Bunsen absorption coefficient is... 

Note that Henry s constant is expressed in various other units, for example, in conjunction with kinetic equations for gas-liquid systems (Section 4.4). If the gas phase concentration is denoted in pressure units (Pa) and the liquid phase concentration in molarity (mol m ), a different unit for Henry s constant is obtained (Ha,c = Pa/ca, Pam mol ). If both the liquid and the gas phase concentrations are expressed as molar fractions, a dimensionless value is obtained for Henry s constant. Therefore, be careful in noting the correct units obtained from the literature. In addition, note that in older literature an absorption coefficient is frequently used, for example, the Bunsen absorption coefficient bu (in ni m bar ) defined as the volume of gas (at 1.013 bar and 0°C) absorbed by one volume of liquid at a certain pressure, for example, 1 bar. Thus bu is inversely proportional to and equivalent to the term /Omoi,iiq 0.0224 m morVWx-... 

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