Search results for "Titration"
showing 10 items of 312 documents
Synthesis and some reactions of linear poly(iminohexamethylene)
1987
By complete reduction of polyamide-6, poly(iminohexamethylene) (PIH) was obtained. This new linear polyamine was characterized by i.r. and by n.m.r. spectroscopy as well as by titration. Differential scanning calorimetry measurements and X-ray diffraction found a high degree of crystallinity whose extent strongly depends upon the pre-treatment. The polyammonium salts that form with inorganic and organic acids show the typical polyelectrolyte effect in viscometry. PIH was alkylated with methyl iodide or acrylic acid and was acylated with N-BOC-l-α-amino acids or N-BOC-ω-amino-alkylenecarboxylic acids. The properties of these derivatives are described.
Arsenite adsorption on goethite at elevated temperatures
2009
Abstract Experimental closed-system ΔT acid–base titrations between 10 °C and 75 °C were used to constrain a temperature-dependent 1-pK basic Stern model of the goethite surface complexation reactions. Experimental data for the temperature dependence of pHPZC determined by the one-term Van’t Hoff extrapolation yield a value for goethite surface protonation enthalpy of −49.6 kJ mol−1 in good agreement with literature data. Batch titration data between 10 °C and 75 °C with arsenite concentrations between 10 μM and 100 μM yield adsorption curves, which increases with pH, peak at a pH of 9, and decrease at higher pH values. The slope of this bend becomes steeper with increasing temperature. A 1…
A119Sn Mössbauer spectroscopic study on complexes of di-and tri-organotin(IV) moieties with 2-mercaptoethanesulfonates, in the solid state and in aqu…
1988
The configuration of the bonding environment of tin in the complexes [R2Sn(SCH2CH2SO3)2]2− (R = Me, Ph) and [Me3Sn(SCH2CH2SO3)]− has been determined to be tetrahedral both in the solid state and in aqueous solution (for the methyl derivatives). The coordination number of tin increases to five in aqueous solutions for the Me2Sn(IV) complexes in Hepes buffer (N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid; at least in fivefold excess, at pH 7.4) due to coordination by the tertiary amino nitrogen atom. No effect is detected due to the surfactant 2-hydroxypropylcellulose concerning both coordination to tin and influence on the Mossbauer parameters. The stoichiometry of mixed complex format…
A program for the simultaneous potentiometric determination of protonation constants and electrode calibration parameters
2005
A program for the potentiometric determination of the protonation constants of mononuclear polyprotic substances is described. A maximum of twelve parameters can be determined simultaneously, including up to six protonation constants, four electrode calibration parameters, the protolysis constant of the solvent and the titrant concentration. Optimization is carried out by using the non-simplified Newton-Raphson method, which is potentiated by the Marquardt algorithm and a distance speeding-up coefficient. A direct search method is also used to improve the initial set of values. Variances are calculated very accurately, since the real Hessian function is used. Statistical weights and ionic s…
Monitoring human parvovirus B19 virus-like particles and antibody complexes in solution by fluorescence correlation spectroscopy
2004
AbstractFluorescence correlation spectroscopy (FCS) was used in monitoring human parvovirus B19 virus-like particle (VLP) antibody complexes from acute phase and pastimmunity serum samples. The Oregon Green 488-labeled VLPs gave an average diffusion coefficient of 1.7x10exp-7 cm(2)s(-1) with an apparent hydrodynamic radius of 14 nm. After incubation of the fluorescent VLPs with an acute phase serum sample, the mobility information obtained from the fluorescence intensity fluctuation by autocorrelation analysis showed an average diffusion coefficient of 1.5x10exp-8 cm(2)s(-1), corresponding to an average radius of 157 nm. In contrast, incubation of the fluorescent VLPs with a pastimmunity se…
Equilibrium and kinetic studies on complex formation and decomposition and the movement of Cu2+metal ions within polytopic receptors
2013
Potentiometric studies carried out on the interaction of two tritopic double-scorpiand receptors in which two equivalent 5-(2-aminoethyl)-2,5,8-triaza[9]-(2,6)-pyridinophane moieties are linked with 2,9-dimethylphenanthroline (L1) and 2,6-dimethylpyridine (L2) establish the formation of mono-, bi- and trinuclear Cu(2+) complexes. The values of the stability constants and paramagnetic (1)H NMR studies permit one to infer the most likely coordination modes of the various complexes formed. Kinetic studies on complex formation and decomposition have also been carried out. Complex formation occurs with polyphasic kinetics for both receptors, although a significant difference is found between bot…
Conformational equilibrium in supramolecular chemistry: Dibutyltriuret case
2015
The association of substituted benzoates and naphthyridine dianions was used to study the complexation of dibutyltriuret. The title molecule is the simplest molecule able to form two intramolecular hydrogen bonds. The naphthyridine salt was used to break two intramolecular hydrogen bonds at a time while with the use of substituted benzoates the systematic approach to study association was achieved. Both, titrations and variable temperature measurements shed the light on the importance of conformational equilibrium and its influence on association in solution. Moreover, the associates were observed by mass spectrometry. The DFT-based computations for complexes and single bond rotational barr…
Hydrolysis of methyltin(IV) trichloride in aqueous NaCl and NaNO3 solutions at different ionic strengths and temperatures
1999
The hydrolysis of methyltin(IV) trichloride (CH 3 SnCl 3 ) has been studied in aqueous NaCl and NaNO 3 solutions (0 < l/mol dm -3 ≤1), at different temperatures (15 ≤ T/°C ≤ 45) by potentiometric measurements (H + -glass electrode). By considering the generic hydrolytic reaction pCH 3 Sn 3+ + qH 2 O = (CH 3 Sn) p (OH) q 3p-q +qH + (logβ pq ), we have the formation of five species and logβ 12 = -3.36, logβ 13 = -8.99, logβ 14 = -20.27 and logβ 25 = -7.61. The first hydrolysis step is measurable only at very low pH values and was not determined: a rough estimate of the hydrolysis constant is logβ 11 = -1.5 (± 0.5). The dependence on ionic strength of logβ pq is quite different in NaNO 3 and N…
Über die bestimmung des zahlenmittels des molekulargewichts von polyoxymethylenen. 36. Mitt. Über polyoxymethylene
1968
Die Bestimmung des Zahlenmittels des Molekulargewichts (Mn) von Polyoxymethylenen durch Osmose, durch Kryoskopie, durch chemische und infrarotspektroskopische Endgruppenbestimmung und durch andere Methoden wird diskutiert. Osmotische Messungen in Phenol bei 90°C gelangen mit Cellophanmembranen besser als mit Glasmembranen. Kryoskopische Messungen nach RAST in Campher ergaben nur in Gegenwart eines Antioxydans zuverlassige Ergebnisse. Zur Endgruppenanalyse wurde vor allem die infrarotspektroskopische Bestimmung von Acetatgruppen weiterentwickelt; zur Auswertung wurde die Intensitat der Carbonylbande bei 5,70 μ in Beziehung gesetzt zu der CH2-Bande bei 6,8 μ und eine Eichung mit Hilfe des Chr…
Mono- and polynuclear hydroxo complexes of monophenylthallium(III)
1974
Summary The hydrolysis of PhTl(OH)ClO4 has been studied in a medium 0.3 M in NaClO4 by a potentiometric technique. The complexes formed by the hydrolysis reactions together with their formation constants have been determined by the general minimizing computer programme LETAGROP. The hydrolysis species observed in the pH range 3–5 are the mononuclear [(PhTlOH)(OH)], the dinuclear [(PhTlOH)2(OH)]+ and the dimer [(PhTlOH)2(OH)2]. The formation constants are log *β11=−4.92±0.2, log *β21=−1.52±0.03 and log *β22=−6.11±0.05. Stepwise reactions are then postulated whose formation constants are respectively log (*β21/*β11)=3.40±0.25, log (*β22/*β21)=−4.59±0.08 and log (*β22/*β112)=3.73±0.09.