No abstract

Articles you may be interested in TES buffer-induced phase separation of aqueous solutions of several water-miscible organic solvents at 298.15 K: Phase diagrams and molecular dynamic simulationsThe activity and osmotic coefficients of aqueous calcium chloride at 298.15 K A critical evaluation of the mean activity coefficient, r + , and osmotic coefficient, ¢>, of aqueous sulfuric acid at 298.15 K is presented for the-molality range of 0 to 28 mol.kg-1 • Osmotic coefficients were calculated from direct vapor pressure measurements, from isopiestic measurements or from freezing point depression measurements. Activity coefficients were calculated from electromotive force measurements of galvanic cells. A least-squares program was used to fit data from all sources using both ¢> and In r ± as functions of molality. A nine parameter equation describes the osmotic coefficient, the mean activity coefficient, and the excess Gibbs energy as a function of the onehalf power of molality. The scientific literature has been covered through January, 1980. Pa (23.767 Torr) (Stimson, 1969, and B T , the second vi rial coefficient for water, vapor, -922 cm 3 .mol-1 from the Steam Tables (Keenan et al ., 1969). Corrections for nonideality of water vapor are given by the second term on the right of eq (1). The gas constant, R, value of 8.31441 J 'moI-1 K -1 was used. The molecular weight of the solvent, M I , and the sum of cations and anions, v, were referenced previously (Staples and Nuttall, 1977).Early measurements of activities of sulfuric acid solu-MOLRLITY IMOL· KG FIGURE 4. Osmotic coefficient vs m l/2 (experimental and calculated).

A buffer solution containing tris(hydroxymethyl)-aminomethane (0.01667 mol/kg) and its hydrochloride salt (0.0500 mol/kg) is proposed as a pH standard for the physiologically important pH range of 7.3 to 7.5. Standard pH values were assigned to this reference solution at temperatures from 0° to 50°C by means of measurements with hydrogen/silver chloride cells without transference. At 37°C, the assigned pH of this buffer solution is 7.382, with a temperature coefficient of -0.026 pH unit per degree Celsius. This new standard is more compatible with biologic fluids than is the previously certified phosphate buffer.

A critical evaluation of the mean activity, Y~" and osmotic coefficients, cj>. of aqueous calcium. chloride at 298.15 K is presented for the concentration range of 0 to 10 mol• kif!. Osmotic coefficients were calculated from direct vapor pressure measurements, from isopiestic measurements or from freezing point depression measurements. Activity coefficients were calculated from electromotive force measurements of galvanic cells. both without liquid'i.unction and with transference, and from diffusion data. A non-linear least-squares program was used to fit data from all sO\lrces using both + and In y* as a function of molality. An eight-parameter .extended Debye-Huckel equation describes the osmotic coefficient, the mean activity coefficient, and the excess free energy as :II. function of molality. The scientific literature has been covered through July, 1976.