Osmotic and activity coefficients of triorganophosphates in n-octane

Abstract

. Can. J. Chem. 60,2755Chem. 60, (1982. Vapor pressure osmometry was used to measure osmotic coefficients for tributylphosphate (TBP), tricresylphosphate (TCP), and triethylhexylphosphate (TEHP) in 11-octane at 30,40,50, and 60°C andat molalities up to0.3 mollkg. Activity coefficients andexcess thermodynamic properties (unsymmetrical definition) were calculated from these osmotic coefficients. At 30"C, the excess Gibbs free energies for 0.1 mol of solute in 1.0 kg 11-octane were -42 J, -66 J, and -20 J for TBP, TCP, and TEHP, respectively. Themore ideal behavior of the TEHP-octane system is attributed to the increasing importance of hydrocarbon-hydrocarbon interactions as the chain length is increased. The excess enthalpies for 0.1 mol of solute in 1.0 kg of solvent were -100 J, -300 J , and -150 J for TBP, TCP, and TEHP, respectively. Thus, association of these solutes arises primarily from entropic effects.Our data could generally be accommodated adequately by postulating association of monomers into dimers. The exception was TCP at lower temperatures, where more complex models were required. Nos donnkes peuvent gentralement s'accomoder de f a~o n adequate en postulant une association de monomeres dans les dimkres. Le TCP fait exception 2 de basses temperatures oh des modkles plus complexes sont necessaires.[Traduit par le journal] 1 Introduction Experimental IThe neutral organic phosphates, particularlyOsmotic coefficients were measured at 30, 40, 50, and 60°Ci tributylphosphate (TBP), are used in many solvent using a CoronaIWescan Model 232A vapor pressure osmom-I extraction processes. In the nuclear industry, such eter. In this apparatus, the steady-state temperature difference is measured between a drop of pure solvent (n-octane) and a I are for the reprocessing of drop of solution, both drops being maintained in a chamber irradiated fuel (1). We have begun a pro-saturated with pure solvent vapor (8,9). Thermistors areused as gram to study interfacial properties rekvant to temperature sensors, and the difference in the voltage develthese solvent extraction systems (2, 3), and thus, oped across the two thermistors, AV, is measured at aconstant we need to know activity coefficients for organic bridge current. The operation of this particular instrument is described in detail by Burge (10). To extend the range of the phosphates in various hydrocarbon and aqueous technique to higher solute molalities, solutions whose osmotic media. The purpose of this work is to measure coefficients were known were used as both reference solution activity coefficients of three triorganophosphates, and vapor-saturating solution. The AV's were obtained relative TBP, tricresylphosphate (TCP), and triethylhexyl-to these reference solutions (11).At each of the four temperatures employed, the instrument phosphate (TEHP)y in '-Octane' Osmotic coef-was calibrated using solutions of n-hexadecane in n-octane as ficients of triorgan0phosphates have been mea-standards (1 I). The voltage difference, AV, was divided by the sured previous...

Osmotic coefficients of trialkyl phosphates in water

“…The constants obtained from these fits are given in Table I and the errors reported are the standard deviations of the fit. If the Bjerrum expression is combined with eq 2, then solute activity coefficients, y2, can be calculated (5,6). The activity coefficients have the standard state which approaches unit activity coefficient as the solute approaches Infinite dilution in the solvent, rather than unit activity for the pure component, as is frequently used for nonelectrolytes.…”

“…Osmotic coefficients were measured at various temperatures by using a Corona/Wescan Model 232 A vapor pressure osmometer. The general principles and operation of this instrument have been described fully by Burge (4) and our procedures have been described previously (5).…”

Osmotic coefficients of triorganophosphorus compounds in n-octane and benzene

“…Osmotic coefficients were measured with a Corona/Wescan Model 232A vapor pressure osmometer. The general principle and operation of the instrument have been described previously (4,6). At each temperature the instrument was calibrated by using n-hexadecane in n -octane, and biphenyl in benzene (4,5).…”

“…The general principle and operation of the instrument have been described previously (4,6). At each temperature the instrument was calibrated by using n-hexadecane in n -octane, and biphenyl in benzene (4,5). Osmotic coefficients were measured to ±0.005.…”