HLPWWW (Version 9.0a) JESS copyright (C) 1985-2025 Licensee : Webmaster, Murdoch University, Australia Welcome. Sunday, 7-Dec-25 22:50 A variety of JESS facilities exist to deal with the physicochemical properties of electrolyte solutions. Such properties include solution densities, heat capacities, activity coefficients, osmotic coefficients, as well as solute properties such as molar volumes, apparent heat capacities and solubilities. More than 50 different properties are recognised. Most of the data concern simple electrolytes, such as NaCl or KOH, but mixed electrolyte solutions of two electrolytes are also covered. Data are available for over 200 solutes (electrolytes and non-electrolytes).
The two most important JESS sub-systems dealing with physicochemical properties are FIZ (a database of property values from the chemical literature) and SIP (a database of Specific Interaction Parameters, mostly Pitzer equation coefficients). These databases can be inspected using the programs VEWFIZ and VEWSIP respectively. Other programs exist to manage these database, such as CHKFIZ, LODFIZ, and LSTFIZ or DMTSIP, MNTSIP, UPDSIP, etc. The general objective of the FIZ sub-system is to link the stored values for recognised solution properties to the particular (bulk) solute or solutes defining the solution and to the prevailing conditions of solute concentration, temperature and pressure. You can display FIZ database values and graphs in Excel spreadsheets. We call this the '8-ball' facility, named after the icon we use to fire it up in Excel. Documentation on how to install this facility can be found in "JesDoc\Manuals\Developers\Excel Interface" (see file "Excel_notes.txt"). The SIP sub-system deals with thermodynamic coefficients for describing physicochemical properties (as a function of T,P,c conditions) using various models, such as Pitzer-type equations. These sets of coefficients can either have been taken directly from the literature or can have been determined by programs such as OPTSIP and FITSIP from the values stored in a FIZ database. The program SIMSIP allows users to calculate selected physicochemical properties as a function of specified conditions using a set of Pitzer equation coefficients stored (previously) in a SIP database. For a single point prediction (for a specified pressure, temperature and concentration of a given electrolyte) values are determined for the mean ionic activity coefficient, the water activity, the osmotic coefficient, the vapour pressure, the apparent molar relative enthalpy, the apparent molar heat capacities (Cp & Cv), the specific heat, the absolute solution density, the relative density difference (wrt H2O), the specific volume and the apparent molar volume. Alternatively, multiple point predictions can be made for a given set of P,T,c conditions and any one of the above properties.
Comprehensive documentatiion on FIZ conventions and FIZ sequential file preparation is available (see 'FIZNAM.DOCX'). You swap between the two main FIZ databases using the DOS Window commands: GOFIZ1 or GOFIZ2.
You can obtain a variety of information about the properties of water using program TSTH2O. These properties include density, compressibility, expansivity, and the dielectric constant (i.e. the static permitivity) and the viscosity. You can also obtain values of the Debye-Hueckel parameters for given temperatures and pressures. Consult the description of the program by searching for "TSTH2O" (without quotes) to obtain further details. For information on the physicochemical properties of pure electrolyte solutions or of seawater consult the index searching for "electrolyte" or "sea".
You can obtain a variety of information about the properties of pure electrolyte solutions using program TSTBEL. These properties include the percentage saturation, density, osmotic coefficient, water activity, and a number of factors for converting concentration scales. Consult the description of the program by searching for "TSTBEL" (without quotes) to obtain further details. Note that the BEL sub-system data are generally inferior to those in the FIZ sub-system. They are currently in the process of being removed, in favour of an alternative approach based on FIZ and SIP. Information about the properties of seawater can be obtained from program "TSTSEA".
The following symbols are used ubiquitously g/L = weight in grams per litre of solution %w/w = weight % = g(solute)/100g(solution) = mass fraction x 100 %w/v = volume % = g(solute)/100mL(solution) %g/g = grams % = g(solute)/100g(solute) M = molarity = mol/L(solution) m = molality = mol/kg(solvent) mol/kg = mol/kg(solution) X = mole fraction 1mol/mol = molar ratio of diln. = 1 mole of solute / moles of solvent
Some physicochemical property terminology: SOLUBILITY refers to the conc. of a saturated solution at given P,t with respect to a specific, well-defined solid phase. SATURATION refers to the practical, most likely, upper limit of concentration of a solution at given P,t with the specified composition regardless of the saturating phase.
Solubility calculations The solubility of a non-aqueous phase in an aqueous solution is defined as the dissolved concentration of that non-aqueous substance (comprising all species which can be formed from it) present when the non-aqueous substance is at equilibrium with the aqueous solution under specified conditions of temperature, pressure and concentrations of other components. Typically, one ion of the dissolved substance will be the limiting factor so the solubility is then obtained from the summed concentration in solution of that ion and its complexes (taking account of the substance's stoichiometry). Solubility is thus determined by the reaction equilibria operating in the aqueous solution. One principal reaction, expressing the equilibrium between the non-aqueous substance and one or more dissolved species, fixes the solubility. Typically, this reaction is called the 'solubility reaction' and its equilibrium constant is called the 'solubility product', Ksp. It is a product of the activities of the ions formed directly from the substance because the non-aqueous phase under standard conditions has unit activity. A high Ksp value indicates a high solubility. Thus, for the solubility of barium sulfate in water, the chemical reaction is: BaSO4(s) = Ba2+ + SO42- where Ksp = {Ba2+} {SO42-} Since barium sulfate is a sparingly soluble solid, the dissolved ion concentrations are very low and, as a good approximation, they often taken to be the corresponding ion activities. Hence, Ksp = [Ba2+] [SO42-]. If Ksp is known (~ 1 x 10-10), the ion concentrations can be calculated because [Ba2+] = [SO42-], so both ~ 1.0 x 10-5 mol dm-3. Conversely, if the solubility is measured, Ksp can be evaluated. Likewise, the solubility of PbCl2(s) can be estimated from Ksp ~ 1.7 x 10-5 noting that if PbCl2(s) is dissolved in water [Pb2+] = 2[Cl-]. However, if an aqueous solution of NaCl is mixed with an aqueous solution of Pb(NO3)2, the solubility of PbCl2(s) depends on which ion is the limiting one, Pb2+ or Cl-. If Pb2+ is in excess, some Pb(NO3)2 will remain in solution but almost all the Cl- will be precipitated. Then, [Pb2+] is determined by the original amount of Pb(NO3)2 less the amount of NaCl introduced; and, [Cl-] can be calculated from [Pb2+] and Ksp. In non-dilute solutions, where the ionic strength and ion specific interactions become significant, the species concentrations cannot be taken as their activities; so, the activity coefficients of the ions participating in the solubility reaction can no longer be taken as unity. They must be calculated using an activity coefficient model. In the above case, for example, the ionic strength is set by the Pb(NO3)2 excess, affecting both {Pb2+} and {Cl-}. For this reason, Ksp values are tabulated at infinite dilution and the corresponding conditional value, Ksp', must be established (from the activity coefficient model) and used in the solubility calculation. Solubility data and tabulated Ksp' values are inherently linked by the choice of activity coefficient model used to evaluate the latter from the former. Another complicating factor is the frequent occurrence of complexes in the solution. For example, PbCl+, PbCl20, PbCl3-, etc. can be formed to a significant extent. Such complexes mean that the solubility of PbCl2(s) is higher than the value calculated from Ksp alone. This is indeed commonplace when solids are not sparingly soluble. To deal with these issues in multicomponent systems, solubility calculations are generally performed by calculating the 'saturation index' (SI), which quantifies the extent to which every solid is dissolved relative to an exactly saturated solution, when SI = 1. The SI value is the ratio of the 'solubility quotient' (Q) over the solubility product, Ksp, where Q is the product of the actual ion activities and Ksp is the product of the ion activities at saturation. Undersaturated solids have SI < 1 and supersaturated solids (in metastable systems) have SI > 1. In other words, when Q < Ksp the dissolving solid has not yet reached the point of saturation and when Q > Ksp saturation has been exceeded and the solid will tend to precipitate in order to achieve equilibrium. The JESS (GEM stages) calculation for an exactly saturated solution of PbCl2(s), cottunite, dissolved in NaCl (3.0 mol dm-1) gives the following result for the solubility at pH = 4. Note that at higher pH the dissolved Pb concentration increases due to the formation of hydroxide complexes. Pre= 1.013 bar Temp= 25 C IStr= 3.36 M pH= 4.00 pe= 5.00 Eh= 296 mV Pb mg/L Pb or moles/L microg/L * % Species ------- ---------- -- ------- 0.05443 11,278 69 Pb+2_Cl-1(6) 0.01104 2,288 14 Pb+2_Cl-1(5) 0.006425 1,331 8 Pb+2_Cl-1(3) 0.005474 1,134 7 Pb+2_Cl-1(4) 0.001115 231 1 Pb+2_Cl-1(2) 0.0001132 23 0 Pb+2_Cl-1 2.834E-6 587 * 0 Pb+2 -------- ---------- -- ------- 0.07860 16,286 100 Total Pb in above species lg(Ksp) lg(SI) Saturation Solid Species ------- -------- ---------- ------------- 4.515 -20.062 Dissolved Lead Pb(s) 27.675 -22.770 Dissolved Lead hydroxide oxide Pb2O(OH)2(s) 73.836 -48.479 Dissolved Trilead tetraoxide Pb3O4(s) 12.814 -10.361 Dissolved Litharge, red PbO(red,s) 12.951 -10.499 Dissolved Massicot, yellow PbO(yellow,s) 49.186 -28.734 Dissolved Lead dioxide PbO2(s) -4.675 0.000 Saturated Cotunnite Pb+2_Cl-1(2)_(s) 8.263 -5.811 Dissolved Lead hydroxide Pb+2_OH-1(2)_(s) 1.720 -0.806 Dissolved Halite Na+1_Cl-1_(s) 20.912 -16.435 Dissolved Sodium hydroxide Na+1_OH-1_(s) 15.802 -11.325 Dissolved Na+1_OH-1_H2O(3.11)_(s) 14.054 -11.602 Dissolved Lead hydroxide am. Pb+2_OH-1(2)_(am.,s) 61.173 -38.268 Dissolved Pb2O3(s) 19.502 -15.025 Dissolved Sodium hydroxide mono. Na+1_OH-1_H2O_(s) 19.102 -14.625 Dissolved Sodium hydroxide dihydrate Na+1_OH-1_H2O(2)_(s) 16.802 -12.325 Dissolved Sodium hydroxide 3.5-hydrate Na+1_OH-1_H2O(3.5)_(s) 16.602 -12.125 Dissolved Sodium hydroxide tetrahydrate Na+1_OH-1_H2O(4)_(s) 1.277 -2.388 Dissolved Laurionite Pb+2_Cl-1_OH-1_(s) 9.189 -7.848 Dissolved Pb+2(2)_Cl-1_OH-1(3)_(s) 13.103 -10.651 Dissolved PbO.0.333H2O(s)