Determination of Air−Water Partitioning of Volatile Halogenated Hydrocarbons by the Inert Gas Stripping Method

Abstract

Air-water partitioning for 21 volatile chlorinated or brominated alkanes, alkenes, and aromatics was measured at 20°C by the inert gas stripping method. Results of the measurements are presented in the form of Henry's law constants (H 12 ), air-water partition coefficients (K aw ), and limiting activity coefficients (γ 1 ∞ ), accurate γ 1 ∞ values being obtained only if accurate pure solute vapor pressure data are available.The halocarbons studied in this work are hydrophobic and exhibit enhanced volatilities from their dilute aqueous solutions representing approximately ranges of γ 1 ∞ from 230 to 70 000 and H 12 from 2 to 70MPa. Correct performance of the stripping method for such systems requires special precautions. As confirmed by test measurements on benzene, chlorobenzene, 1,1,1-trichloroethane, and 1,1,2-trichloroethane, the complete equilibration in the stripping cell can be achieved under vigorous mixing of the cell, low stripping gas flow rates (approximately 10 cm 3 ‚min -1 ), and low relative elution rates (0.01 min -1 ). Choosing for each system a cell of a suitable volume made it possible to comply with the latter requirement. The results compare well with recent literature values obtained by various methods for some of the halocarbons. For two selected halocarbons (bromobenzene and 1,1-dichloroethane), detailed measurements of the temperature dependence of air-water partitioning were carried out in the range of (10-50)°C. These measurements corresponding to the range of H 12 from 5 to 72 MPa provide additional support for the validity of the method.

Infinite dilution activity coefficients for benzene and toluene in water and in aqueous solutions of the protein denaturants urea and guanidine hydrochloride

“…The experimental setup and procedure used in this work are essentially the same as those we have used recently to measure (air, water) partitioning of halocarbons and described in detail elsewhere. (12) The apparatus is designed around a computer interfaced Hewlett-Packard gas chromatograph, Model 5890 II, equipped with a flame ionization detector and a pneumatically operated six-port gas sampling valve which is housed in an independently heated zone of the g.c. and kept at T = (433 ± 1) K. The equilibrium stripping cell is an all-glass jacketed device comprising the dilution cell that holds the dilute solution under study.…”

“…For a detailed view of the cell design, we refer to figure 2 of our recent paper on i.g.s. (12) The cell is thermostated by an electronic water-circulating bath (Lauda, Model RC6 CP) to ±0.02 K. The temperature of the water bath is measured with a calibrated standard mercury thermometer (Karl Schneider, Wertheim, F.R.G.) to ±0.01 K. The constant flow of stripping gas (N 2 ) is supplied by an auxiliary channel of the g.c.…”

“…method. The technique of i.g.s., which has been proved to be highly reliable for similar systems, (12) has distinct advantages over some other methods: broad range applicability; high accuracy; no need to calibrate the gas chromatograph detector; and no need to know exactly the initial solute concentration.…”

Automated analyser for monitoring trace amounts of volatile chloro‐organic compounds in recirculated industrial water

“…The instrument utilizes the purge and trap principle [1± 5], which is particularly suitable for the isolation of volatile chloro-organic compounds from water [3,6,7], and, hence, operates in a periodic mode. It was decided to utilize not the total stripping but rather a dynamic one, when the liquid sample and the stripping gas, both at constant¯ow rates, come into contact with each other in a countercurrent purging bubbler, where the volatile chloro-organic compounds are divided between the two phases with their respective partition coeae cients [6] kept constant by maintaining the temperature at 25 § 2 8C.…”

Infinite dilution activity coefficients for toluene in aqueous solutions of the protein stabilizers glycerol, ethylene glycol, glucose, sucrose and trehalose

“…This is the strategy we have followed in this work using the inert gas stripping (IGS) method which has been proved to be highly reliable for similar systems. (8,10) In this work we present experimental infinite dilution activity coefficients for toluene in aqueous solutions of glycerol, ethylene glycol, glucose, sucrose and trehalose, over the temperature range 273 K to 323 K. The concentrations of these stabilizers were chosen to match as closely as possible those used in the biochemistry field. For glycerol, the data were measured at four concentrations (0.5 mol · dm −3 to 5.0 mol · dm −3 ); at the highest glycerol concentration, γ ∞ 1 was also determined at T = 268 K. Ethylene glycol, glucose and sucrose were used at a single concentration (1.5 mol · dm −3 ).…”