MUTUAL RELATIONSHIP OF HENRY'S LAW CONSTANTS AND AQUEOUS PHASE CONCENTRATIONS FOR BENZENE,TOLUENE AND O-XYLENE AT 30 ° C

摘要

Dimensionless Henry's law constant in water at 30 °C ranged from 0.272 ± 0.015 to 0.340 ± 0.008 for benzene as the equilibrium aqueous phase concentrations ranged from 0.546 ± 0.003 to 329 ± 1 mg/dm~3. A decrease in the Henry's law constant to 0.190 ± 0.002 was recorded be-tween 329 ± 1 and 1370 ± 3 mg/dm~3, but the results of the Dixon test at 1 % level of significance indicated that this value was a statistically significant outlier. Therefore Henry's law constant of benzene was independent on the dissolved aqueous phase of benzene and the average value of 0.312 ± 0.022 is recommended for practical purposes. For toluene, the equilibrium aqueous phase concentration ranged from 3.42 ± 0.05 to 420 ± 4 mg/dm~3 and dimen-sionless Henry's law constants varied between 0.170 ± 0.011 and 0.321 ± 0.007. In the case of o-xylene, equilib-rium aqueous phase concentrations ranged from 3.03 ± 0.03 to 123.9 ± 0.3 mg/dm~3 and Henry's law constants ranged from 0.120 ± 0.004 to 0.268 ± 0.008. Using Kruskal-Wallis analysis of variance by ranks and the Mack-Wolfe test for ordered alternatives, the Henry's law constant increased up to 6.78 ± 0.04 mg/dm~3 for toluene. For o-xylene, Henry's law constant was independent of dissolved concentration up to 6.96 ± 0.05 mg/dm~3. Henry's law constants decreased with increasing equilibrium aqueous phase concentration at higher values for toluene and o-xylene. Hydrogen bonding between water molecules and the aromatic hydrocarbon molecules provides a possible explanation for the observed trends.