Search results for "Pitzer equations"
showing 8 items of 8 documents
Modeling S-carboxymethyl-L-cysteine protonation and activity coefficients in sodium and tetramethylammonium chloride aqueous solutions by SIT and Pit…
2007
Solubility and acid–base properties of S-carboxymethyl-l-cysteine (carbocysteine, ccys) in NaClaq and tetramethylammonium chloride, (CH3)4NClaq ,a tt =2 5 ◦ C and at different ionic strengths were investigated. Solubility was studied at 1.0 ≤ I (mol L −1 ) ≤ 5.0 for NaClaq and 1.0 ≤ I (mol L −1 ) ≤ 3.0 for (CH3)4NClaq, while potentiometric measurements (by ISE-H + , glass electrode) were performed at 0.1 ≤ I (mol L −1 ) ≤ 5.0 for NaClaq and 0.5 ≤ I (mol L −1 ) ≤ 3.0 for (CH3)4NClaq. Solubility data allowed us to determine Setschenow constants and activity coefficients of neutral carbocysteine (H2ccys). Dependence on ionic strength and ionic medium of protonation constants and activity coeff…
Modeling ATP protonation and activity coefficients in NaClaq and KClaq by SIT and Pitzer equations.
2006
Abstract The acid–base properties of Adenosine 5′-triphosphate (ATP) in NaCl and KCl aqueous solutions at different ionic strengths (0 I / mol L − 1 ≤ 5 for NaCl aq , 0 I / mol L − 1 ≤ 3 for KCl aq ) and at t = 25 °C were investigated. A selection of literature data on ATP protonation constants and on activity isopiestic coefficients was performed, together with new potentiometric measurements (by ISE-H + , glass electrode). Both literature and new experimental data were used to model the dependence on ionic strength and ionic medium of ATP protonation by SIT (Specific ion Interaction Theory) and Pitzer equations. In addition to values of first and second ATP protonation constants in…
The interaction of amino acids with the major constituents of natural waters at different ionic strengths
2000
Abstract The interaction of amino acids with the major constituents of natural waters has been studied potentiometrically by determining protonation constants at different ionic strengths (e.g., I ≤5.6 mol (kg H 2 O) −1 (NaCl)) and in artificial seawater (containing Na + , K + , Ca 2+ , Mg 2+ , Cl − and SO 4 2− ) at different salinities. For glycine determinations in mixed NaCl–MgCl 2 , electrolyte solutions were also performed. The data included in this work, together with some already published, make it possible to calculate parameters for dependence on ionic strength using different models, i.e. an extended Debye–Huckel type equation and Pitzer equations. The results can be interpreted b…
Protonation of Carbonate in Aqueous Tetraalkylammonium Salts at 25°C.
2006
Protonation constants of carbonate were determined in tetramethylammonium chloride (Me4NClaq 0.1≤I/mol kg−1 ≤4) and tetraethylammonium iodide (Et4NIaq 0.1≤I/mol kg−1 ≤1) by potentiometric ([H+]-glass electrode) measurements. Dependence of protonation constants on ionic strength was taken into account by modified specific ion interaction theory (SIT) and by Pitzer models. Literature data on the protonation of carbonate in NaClaq (0.1≤I/mol kg−1 ≤6) were also critically analysed. Both protonation constants of carbonate follow the trend Et4NI>Me4NCl > NaCl. An ion pair formation model designed to take into account the different protonation behaviours of carbonate in different supporting electr…
Liquid–liquid equilibria in the system H3PO4–KCl–H2O–tri-n-butyl phosphate: experiments and modelling
2004
Abstract The liquid–liquid equilibria of the system H3PO4–KCl–H2O–TBP was studied experimentally in the concentration range 0–6 mol/kg. The obtained data were modelled using the Pitzer equation for the aqueous phase and the Sergievskii–Dannus relationship for the organic phase. A fairly good agreement was observed between the model and the experimental data.
Hydrolysis and chemical speciation of (C2H5)2Sn2+, (C2H5)3Sn+ and (C3H7)3Sn+ in aqueous media simulating the major composition of natural waters
2001
The hydrolysis of (C 2 H 5 ) 2 Sn 2+ , (C 2 H 5 ) 3 Sn + and (n-C 3 H 7 ) 3 Sn + has been studied, by potentiometric measurements ([H + ]-glass electrode), in NaNO 3 , NaCl, NaCl/Na 2 SO 4 mixtures and in a synthetic seawater (SSWE), as an ionic medium simulating the major composition of natural seawater, at different ionic strengths (0 ≤ I ≤ 5 mol dm -3 ) and salinities (15 ≤ S ≤ 45), and at t = 25 °C. Five hydrolytic species for (C 2 H 5 ) 2 Sn 2+ , three for (C 2 H 5 ) 3 Sn + and two for (C 3 H 7 ) 3 Sn + are found. Interactions with the anion components of SSWE, considered as single-salt seawater, are determined by means of a complex formation model. A predictive equation for the calcul…
Modeling the acid-base properties of molybdate(VI) in different ionic media, ionic strengths and temperatures, by EDH, SIT and Pitzer equations
2017
This paper reports the results of a study on the determination of the protonation constants of MoO42 −, in NaClaq, NaNO3aq, KClaq, at different ionic strengths (0 < I/mol dm− 3 ≤ 5.0 in NaClaq, 0 < I/mol dm− 3 ≤ 3.0 in NaNO3aq and KClaq) and temperatures (278.15 ≤ T/K ≤ 318.15 in NaClaq, only 298.15 K in NaNO3aq and KClaq), by potentiometric (ISE-H+ glass electrode) and spectrophotometric (UV/Vis) titrations. After a critical analysis of results and literature findings, the proposed speciation model takes into account the formation of two monomeric and four heptameric species, namely: MoO4H−, MoO4H2, (MoO4)7H86 −, (MoO4)7H95 −, (MoO4)7H104 − and (MoO4)7H113 −. Due to the complexity of…
Hydrolysis of (CH3)Hg+ in Different Ionic Media: Salt Effects and Complex Formation
1998
The hydrolysis of monomethylmercury(II) was studied potentiometrically, in NaNO3, Na2SO4, and NaCl aqueous solution, in a wide range of ionic strengths (NaNO3, 0 ≤ I ≤ 3.25; Na2SO4, 0 ≤ I ≤ 1; NaCl, 0 ≤ I ≤ 3 mol dm-3) and at t = 25 °C. For the reaction (CH3)Hg+ = (CH3)Hg(OH)° + H+, we found log K1 = −4.528 (I = 0 mol dm-3). The species [(CH3)Hg]2(OH)+ was also found, with log β2 = −2.15. Monomethylmercury(II) forms quite strong complexes with Cl- (log K = 5.45, I = 0 mol dm-3) and SO42- (log K = 2.64, I = 0 mol dm-3). The dependence on ionic strength of formation constants was considered by using a Debye−Huckel type equation. Hydrolysis and complex formation constants (at different ionic s…