Molal Units Research Articles

Strange behaviour of the methyl diphenyl phosphate-Cu(NO 3) 2 complex

Methyl diphenyl phosphate (MDPP) was used in our laboratory for extraction of acids [1, 2] and nitrates of uranium, thorium, zinc and copper [3, 4]. The striking property of MDPP is its ability to form solid complexes with inorganic salts [5]. Extraction-equilibrium in the copper nitrate-water-undiluted MDPP system is consistent with formation of partially dissociated Cu(NO 3) 2(H 20) 3- (MDPP) 3 complex with the equilibrium constant ∼4·10 −6 in molal units [3]. Considering the optical properties of extraction systems, it was observed that only in the case of Cu(NO 3) 2 exists, unusually, time dependent optical activity of the organic phase. There is no absorption in u.v. region when freshly prepared (equilibration of 0.1 N Cu- (NO 3) 2 with undiluted MDPP, after separating the concentration of copper is about 6 mg Cu(NO 3) 2/I of MDPP), highly diluted with benzene and the organic phase measured against benzene. Methyl diphenyl phosphate itself has benzoid absorption band at 220– 270 mm [6]. However, when the organic phase is exposed to the day-light for a period of ∼24 hrs., or when the sample remains for 10–15 min. in spectrophotometer, suddenly a very strong (ϵ ∼ 10 5, broad absorption band with maximum at 305 mm appears and irregular decay of it is observed. Sometimes, repeated irradiations of the sample during the decay period influence significantly the decay-curve, however in any case, the life-time of intermediate species responsible for the reported behaviour does not exceed 2–3 days. It is worth to note, that the organic phase is optically inactive when copper nitrate is replaced by copper sulphate or chloride and the role of oxygen (irradiation with and without the gas) is uncertain. In this stage of investigation, the formation of relatively long-lived Cu(III) complex is postulated, based on some similarity with the copper(III)-peptide complex reported by Margerum [7].

The estimation of acid dissociation constants in seawater media from potentionmetric titrations with strong base. I. The ionic product of water — Kw

Abstract The various assumptions implicit in the calculation of acid dissociation constants (based on ionic medium standard states) from potentiometric titrations using a cell with liquid junction (i.e. a pH measuring cell) have been examined. It was concluded that results can be obtained having an accuracy commensurate with the experimental precision. It has been shown that although the precise composition of the medium is a function of the hydrogen ion concentration (because of the protolytic nature of some of the ions in the media, e.g., sulphate and fluoride), the effect of such variations in the medium composition can be compensated for when defining the activity of hydrogen ion on an ionic medium standard state by defining the concentration of hydrogen ion as: [H] SWS =h(1 + β HSO 4 ST + β HF E T ) where βHSO4 and βHF are the relevant association constants and ST and FT are the total concentrations of sulphate and fluoride, respectively. This approach was used to obtain values for the ionic product of water (KW) in artificial seawater media at various temperatures and ionic strengths. These were fitted to give the equation (molal concentration units): pK w = 3441.0 T +2.256-0.7091 1 2 ( rms deviation 0.01 ) where I is the formal ionic strength of the artificial seawater medium and T is the absolute temperature. The values obtained are in reasonable agreement with those found by previous workers.

The ionization constant of nitric acid at high temperatures from solubilities of calcium sulfate in HNO 3H 2O, 100–350°C; activity coefficients and thermodynamic functions

Solubilities of calcium sulfate have been determined in aqueous nitric acid solutions to high molalities at temperatures from 100 to 350°C. Equations were developed for obtaining ionization quotients ( Q n ) of nitric acid from the solubilities with the use of second ionization constants of sulfuric acid and solubility product constants of calcium sulfate together with their activity coefficients. By Debye-Hückel extrapolations of Q n ionization constants ( K n , molal units) of nitric acid were obtained. These constants agreed with earlier values from raman spectra [Krawetz (1955) at 0, 25, and 50°C] and electrical conductance [Noyes et al. (1907) at 218 and 306°C]. Uncertainties, however, in K n at 350°C may have resulted from reversible decomposition of the acid or hydrolysis of Ca 2+. Values of K n ′ (molar units) decrease from 45 at 0°C to about 0·003 at 350°C, which is 3–5 times lower than ionization constants of 1-1 salts at 350°C. The equation for the variation of K n ′ with temperature of Young et al. (1959) is substantiated, and thermodynamic functions are calculated. Activity coefficients for both CaSO 4 and HNO 3 equilibria are obtainable from the results. These activity coefficients may be used to calculate solubilities of CaSO 4 in other high-temperature mixed electrolyte systems. The dominant species present in the system studied are presented for both low and high temperatures.

Solution of problems involving conventional and complex distillation columns at unsteady state operation

AbstractThe θ method of convergence has been applied to conventional and complex columns at unsteady state operation. A different holdup for each stage may be specified in terms of molal, mass, or volumetric units. Plate efficiencies were used, and the K values and enthalpies were taken to be polynomials in temperature.

Heats of Mixing, Liquid Heat Capacities and Enthalpy-Concentration Charts for Methanol-Water and Iso-propanol-Water Systems

The measurements of heat of mixing and liquid heat capacity at various tempratures and concentrations were performed for the systems, methanol-water and iso-propanol-water, at 1 atm. The object of the experiments was to obtain the basic data available for constructing enthalpyconcentration charts and for checking thermodynamic consistency of vapor-liquid equilibrium data at various pressures which will be reported in another paper.New methods were adopted for the measurements, especially for the measurement of exothemic mixing and heat capacity. Experimental data obtaind are given in Figures 4, 5, 7 and 8, and Tables 1, 2, 5 and 6, and smoothed values, in Tables 3, 4, 7 and 8. The values of heat of mixing for iso-propanol-water system at temperatures other than 20°C, given in Table 8, were calculated from the values of heat of mixing at 20°C and the smoothed values of heat capacity for the system. The values of heat capacity of pure alcohols were somewhat higher than those of I.C.T., but the value for iso-propanol at 50°C was lower. The plots of expansion factor vs. heat capacity were made to check the applicability of Eq.(1), derived by Chow and Bright as a general correlation for liquid of a pure component. Figure 6 shows that the equation mostly holds good not only for pure alcohols but also for the mixtures of alcohols and water at high alcohol concentration, especially at higher temperatures. The poor correlation of Eq.(1) at low concentration may be due to some peculiar properties of water.Enthalpy-concentration charts for the two systems at 1atm. were constructed on molal units by the use of the data obtained from this experiment and of other properties from the literature. Figures 10 and 11 show the charts, and Tables 10 and 11 give the calculated values, the datum level for the enthalpies being chosen as pure liquids at 0°C and 1 atm.Using these charts, comparison was made between the numbers of the theoretical plates of a distillation column by the Ponchon and the McCabe methods, and the effect of heat loss from column wall on the number of theoretical plates of the Ponchon method was studied. For alcoholwater systems the McCabe method always gives fewer number of plates than the Ponchon method. Figure 11 shows the comparison between the results by these two methods applied to the methanolwater system.

Standard Entropy of Adsorption

WE have recently shown1, by a thermodynamical procedure, how the standard free energy of adsorption of a solute on to a solution/air interface (δ G°) may be obtained from the limiting slope α at low concentrations of the surface tension-concentration curve. This is given by the equation where α is—(dy/dc)c=0 and δ is the thickness of the surface layer, which was identified with the most probable length of the adsorbed molecule. The standard states in bulk and on the surface are hypothetical states in which the solute is at unit activity in each (activity is expressed in molality units), but essentially have all the properties of infinitely dilute solutions.