Theory of Titration Curves. Part I. The locations of inflection points on acid-base and related titration curves

Ionic Equilibria and pH reviews the quantitative aspects of aqueous acid-base chemistry. Definitions and concepts are presented and appropriate worked examples illustrate calculations of concentration, pH and ionization constants. Acid-base properties of salts (salt hydrolysis) is introduced and explained along with the common-ion effect and calculation of hydrolysis constants. Equilibria of acid-base buffers with respect to buffer preparation, calculating the pH of a buffer solution and application of the Henderson-Hasselbalch equation, buffer range and buffer capacity is discussed. Determining the pH during acid-base titrations, selecting the appropriate acid-base indicators, and generating pH titration curves are explained.

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Shape of acid–base fluorescence emission titration curves in the presence of buffer and quenching effects

Journal of the Chemical Society Faraday Transactions ◽

10.1039/ft9969200957 ◽

1996 ◽

Vol 92 (6) ◽

pp. 957-968 ◽

Cited By ~ 12

Author(s):

Maria João Melo ◽

M. Alexandra Bernardo ◽

Eurico C. Melo ◽

Fernando Pina

Keyword(s):

Fluorescence Emission ◽

Acid Base ◽

Titration Curves

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Acid dissociation constants of glycopeptides

Biochemical Journal ◽

10.1042/bj1630031 ◽

1977 ◽

Vol 163 (1) ◽

pp. 31-38 ◽

Cited By ~ 1

Author(s):

B M Austen ◽

R D Marshall

Keyword(s):

Amino Acid ◽

Dissociation Constants ◽

Acid Dissociation ◽

Hydroxyl Group ◽

Amino Acid Residues ◽

Acid Base ◽

Titration Curves ◽

Pka Value ◽

Hen’S Egg ◽

Additional Amino Acid

Glycopeptides containing mainly four amino acid residues in the sequence Asn-Leu-Thr-Ser, with small amounts of additional amino acid residues, were isolated from enzymic hydrolysates of hen's-egg albumin. Heterogeneity of the carbohydrate moiety was confirmed. Acid-base titrations showed that the alpha-amino group has a pKa value of 6.43 at 25 degrees C. The standard free engery and entropy changes associated with the ionization at 25 degrees C were 37.2kJ-mol-1 and -0.014kJ-mol-1- K-1 respectively. The complications arising in the interpretation of titration curves of the glycopeptides, which are heterogeneous with respect to the peptide chain, were considered and discussed in the light of the earlier suggestion that the titration curve of the glycopeptide might be interpreted as being due in part to a structure in which the hydroxyl group of the threonine residue is hydrogen-bonded to the beta-aspartamido oxygen atom [Neuberger & Marshall (1968) in Symposium on Foods - Carbohydrates and their Roles (Schultz, H.W., Cain, R.F. & Wrolstad, R.W., eds.), pp. 115-132, Avi Publishing Co., Westport, CT]. It is concluded that either the glycopeptides do not contain a hydrogen bond of that type, or, if they do, that it cannot be recognized by acid-base-titration studies.

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Equivalence Points and Inflexion Points in Acid-Base Titration Curves

Australian Journal of Chemistry ◽

10.1071/ch9630759 ◽

1963 ◽

Vol 16 (5) ◽

pp. 759 ◽

Cited By ~ 5

Author(s):

RH Stokes

Keyword(s):

Strong Acid ◽

Ionization Constants ◽

Weak Acids ◽

Acid Base ◽

Strong Base ◽

Titration Curves ◽

Acid Base Titration

General equations are derived for the relation between pH and stoichiometric degree of neutralization in the titration of monoprotic and diprotic weak acids (or bases) with strong acid or strong base. From these equations the number and position of inflexion points in the curves is derived, and their relation to the equivalence points is shown. Methods for determining ionization constants from inflexion points are discussed.

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Na+ and K+ Binding by Fulvic Acid

Canadian Journal of Chemistry ◽

10.1139/v73-481 ◽

1973 ◽

Vol 51 (19) ◽

pp. 3217-3222 ◽

Cited By ~ 32

Author(s):

Donald S. Gamble

Keyword(s):

Aqueous Solution ◽

Fulvic Acid ◽

Free Energies ◽

Acid Base ◽

Titration Curves ◽

Electrostatic Binding ◽

Binding Regions

The electrostatic binding of Na+ and K+ by fulvic acid in aqueous solution has been measured with cation electrodes at 25.00 °C ± 0.05. The binding equilibria were followed during the course of acid–base titrations, and have revealed distinct binding regions in the titration curves. In one of these regions Na+ is more strongly bound than is K+. The standard free energies of binding were 11.7 × 103 to 20.5 × 103 J/mol ± 2% for Na+, and 11.5 × 103 to 17.8 × 103 J/mol ± 1%, for K+.

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BUFFER SYSTEMS BASED ON AMINOMETANESULPHONATE AND MONOETHANOLAMMONIUM N-ALKYLAMINOMETHANESULPHONATES

Odesa National University Herald Chemistry ◽

10.18524/2304-0947.2021.2(78).233816 ◽

2021 ◽

Vol 26 (2(78)) ◽

pp. 22-31

Author(s):

R.E. Khoma ◽

А. А-А. Ennan ◽

T. S. Bienkovska ◽

L. T. Osadchiy ◽

E. L. Roy

Keyword(s):

Buffer Capacity ◽

Acid Base ◽

Ph Buffering ◽

Ph Values ◽

Titration Curves ◽

Upper Limit ◽

Empirical Function ◽

Ionic Associates ◽

Aminomethanesulfonic Acids ◽

Acidic Region

The limits of the pH buffering action (pHbuff) of YNHCH2SO3H – NH2CH2CH2OH –H2O (Y = H, CH3, HOCH2CH2, t-С4H9 and C6H5CH2) were determined and their buffer capacity (p) for monoethanolamine (MEA) was estimated in the temperature range 293–313 K. For systems with aminomethanesulfonic acid (AMSA), its N‑methyl, N‑hydroxyethyl (HEAMSA) and N‑benzyl (BzAMSA) derivatives, an increase in temperature leads to a decrease in the pH values of the lower limit of the buffering action of their solutions with monoethanolamine; in the case of N‑tert-butylaminomethanesulfonic acid (t-BuAMSA) – to an increase in the specified characteristic. An increase in temperature for systems with the most hydrophobic t-BuAMSA and BzAMSA (in comparison with other studied aminomethanesulfonic acids) leads to a decrease in the pH values of the upper limit of the buffer action. A decrease in the YNHCH2SO3H and NH2CH2CH2OH concentration leads to a shift in the boundaries of the pH of the buffering action to a more acidic region. The nature of the influence of the empirical function, combining their acid-base properties and lipophilicity (рKа + lgPow), on the concentration dependence of the buffer capacity according to MEA was revealed. It is shown that the buffering effect of the studied systems is due to the presence, in addition to the systems N‑alkylammoniummethanesulfonate – N‑alkylaminomethanesulfonate and 2-hydroxyethylammonium – monoethanolamine, ionic associates (pairs and triples). The position of the extrema on the graphical π=f(CMEA)/QYAMSA) dependencies for systems with hydrophilic AMSA and HEAMSA coincides with the position of the first minima on the differential titration curves dpH/dV = f(CMEA)/QYAMSA). Substitution of MEA to potassium aminomethanesulfonate leads to a shift in the pH buffering action to a more acidic region and increases the buffer capacity of the resulting systems.

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