Objectives of the Solubility Data Series Mark Salomon MaxPower, Inc. 141 Christopher Lane Harleysville, PA 19438 [email protected]Foreword by A.S Kertes appearing in SDS Volumes 1-53 (1979-1993). “If the knowledge is undigested or simply wrong, more is not better.”
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company reports are generally uncritical, limited in literature
survey, neglect error limits and lack references which users might
wish to check.
•
The Solubility Data Project and the Solubility Data
Series
• The IUPAC Solubility Data Project (SDP) addresses the above problems by producing the Solubility Data Series (SDS) in which all available published literature to date on solubility data from all available literature sources for a specific solute/solvent system are precisely detailed on Compilation(data) sheets providing information on materials, experimental methods and errors. Where sufficient literature data exist, contributors to the SDS provide Critical Evaluationscomparing literature data to determine their merits. Data can be classified as rejected when qualitative or incorrect, recommended when agreement between different authors exists, or tentative when sufficient literature comparisons cannot be made.
• Details on preparing Compilations and Critical Evaluations are presented in the following slides.
General Format for Compilations (Data Sheets)
Components:
List of components: formulas, CAR
numbers
Original Measurements:
Citation to the primary source of data
Variables:
Temperature, pressure, concentrations
Prepared by:
Name of Compiler
Experimental Values
Experimental data exactly as they appear exactly in the literature and
converted to various convenient units where appropriate.
Auxiliary Information
Method/Apparatus/Procedure:
Experimental apparatus and methods used to determine solubilities.
Source and Purity of Materials:
Estimated Error:
Either from the primary source or estimated by the compiler.
General Format for Critical Evaluations
Components:List of components: formulas, CAR
numbers
Evaluator:
Name of Evaluator and date of
evaluation
Based on data in the compilations, the Evaluator discusses the data in
terms of experimental methods, purity of materials, reproducibility and
precision or accuracy. If sufficient data exist by different authors, the
Evaluator will produce a set of data based on weighted averages or an
appropriate smoothing equation with estimated standard deviations.
The data in this set are designated as either Recommended or
Tentative. Data that are judged to be of low precision or in error are
either rejected or designated as Doubtful.
Graphical plots of Recommended or Tentative data are given where
appropriate.
Examples of Smoothing Equations used in Critical Evaluations
(mole fraction bases for binary gas/liquid & solid/liquid systems)
1ln 1 ( ) / (1 ) A B Cln Drv v r r v rx x v r r r x T T T
1 = A B Cln DY T T T
Clarke and Glew’s variation* of the van’t Hoff equation for solubilities at constant
pressure is used extensively in the Critical Evaluations;
The solubility function Y is formulated either in mole fraction or molality units. Mole
fraction units are useful for solubilities over the entire composition range from very
dilute solutions, including hydrates, to the melting point of the anhydrous solid in
which case the above equation takes the form (Counioux, Cohen-Adad, Lorimer).
For gas solubilities as a function of pressure at constant temperature,
the following equation has been used (Battino et al.)
2
0 1 2ln A ln / MPa A / MPa A / MPax P P P
*E.C.W. Clarke and D.N. Glew, Evaluation of thermodynamic functions from equilibrium
constants, Trans. Faraday Soc., 62, 539 (1966).
Examples of Smoothing Equations used in Critical Evaluations
(molality bases for binary solid/liquid systems)
A second and equivalent form of the function Y is useful when hydrates are the solid
phase in which case the above equation takes the following form (Counioux, Cohen-Adad, Lorimer, Mioduski et al.)
1 = A B Cln DY T T T
1
0 0ln( / )-( / -1) = A B Cln Dm m m m T T T
Where m0 = 1/rM2 is the molality of a binary salt solvate with M2 the molar mass of the
solvent. This equation is particularly useful to accurately confirm and predict metastable solubilities
before and after congruent melting points. Other complex methods involving equations for
activity coefficients are used providing additional experimental data exist. For example, the
solubilities of the alkaline earth carbonates MgCO3 and BeCO3 utilized the equation
23
2 2 2s c 1 w
1 2
2 M HCO
CO CO CO41 1lg lg lg lg lg lg
mol kg 3 3 atm atm atm
f f fK K K as ca b d T
K T
where Ks is the solubility constant of MCO3, Kc is the solubility constant of CO2, K1 and K2
are the first and second acid dissociation constant of CO2/carbonic acid, f(CO2) is the
fugacity of CO2, and the values are activity coefficients (De Visscher et al.).
Very Old Solubility StudiesSolubilities published even in the first half of the 19th century often compare favorably
with values measured recently and sometimes constitute the only source of data.
Compilations based on these publications not only are possible sources of reliable data
but also are sources for the history of science and technology. Example of a
compilation for NaCl + H2O published in 1885 where solubilities were determined to
be Recommended with experimental methods and purity of materials comparable to
modern standards is summarized in the following 3 slides.
Example of a compilation for NaCl + H2O published in 1885
A / Bln( / ) C DfY T T T T
From R. Cohen-Adad and J.W. Lorimer, Solubility Data Series, Volume 47. For the critical evaluation
of the binary NaCl-water system, 481 data sets fitted by least squares, and after rejecting outliers,
409 data points fitted to the 4-parameter equation to produce a set of Recommended and
Tentative solubilities as a function of temperature.
where Tf is a reference temperature (melting point of the solid phase). Selected results for
data reported by Raupenstrauch in 1885 are shown below.
Examples of Smoothing Equations used in Critical Evaluations
(mole fraction bases for liquid/liquid systems)
(1/3)
1 c,1 1 c 2 c 3 cln ln ( / 1) (1 / ) (1 / )x x b T T b T T b T T
(1/3)
2 c,1 1 c 2 c 3 cln ln(1 ) ( / 1) (1 / ) (1 / )x x c T T c T T c T T
For binary systems where Tc is the upper critical solution
temperature and xc,1 is the corresponding critical mole
fraction, the solubility of liquid 1 in liquid 2 analyzed by
(Góral et al., SDS vol 91) utilized the following equation
The solubility of liquid 2 in liquid 1 is given by
For ternary systems, experimental data were correlated
using the NRTL equation (Góral et al., SDS vol 101 based on
the notation of Renon and Prausnitz, AIChE J. 14, 135 (1968))
åå
å=
3
3
3
R i
k
kki
j
jjiji
i
E
xG
xG
xT
Gt
Future of the SDP
At the present time, 103 SDS volumes have been published and new volumes are in various stages of completion. A number of volumes are quite large and thus have been published in parts in JPCRD bringing the total number of SDS publications to 136.
New contributors to the SDS are warmly welcome, and inquiries can be sent to the following:
• Clara Magalhães, Chair of the Subcommittee on Solubility and Equilibrium Data (SSED). Email: [email protected]