| Popis: |
The variation in water content of tri-n-octylamine (TOA) and several of its salts with water vapor pressure was determined by isopiestic and liquid-liquid equilibrium. In addition, the type of bonding was investigated with infrared absorption. Water was determined by Karl Fischer titration, by weight gain, and by use of titrated water as an analytical tracer. Benzene solutions of TOA extract water to form the monohydrate, with no indication of the formation of a dimer hydrate even at 0·5 M TOA. The value obtained for the equilibrium quotient with its standard error of fitting is 0·858 ± (σ = 0·006). At a fixed amine concentration, the water extracted by TOA bisulfate (TOAHS) varied nearly linearly with water activity up to aw = 0·9. That extracted by the normal sulfate (TOAS) and mixed TOA-TOAS also varied linearly with aw up to 0·4–0·7, then increased more steeply. The effect of hydration at saturation (aw = 1) depended on the amine salt form and concentration. There was little difference between benzene and phenylcyclohexane as diluents. In undiluted TOAS, water molarity varied linearly with aw up to aw = 0·7), but the mole fraction of water did not follow Henry's law above aw = 0·2). In this binary system, both TOAS and H2O showed negative deviations from Raoult's law. Infrared absorption spectra suggest both hydrogen bonding of water to the anion and simple dissolution of unbonded water, but indicate no direct interaction between the oxygen of the water and the alkylammonium ion. Benzene solutions of other TOA salts tested extract less water than solutions of TOAS, Cl > NO3 > ClO4 > OAc. They follow Henry's law, from aw = 0 to 0·85 for the nitrate and to aw = 1 for the others. |
