Catalytic Thermometric Titrimetry Research Articles

Determination of the Acidity of Oils Using Paraformaldehyde as a Thermometric End-Point Indicator

The determination of the acidity of oils by catalytic thermometric titrimetry using paraformaldehyde as the thermometric end-point indicator was investigated. The sample solvent was a 1:1 (v/v) mixture of toluene and 2-propanol and the titrant was 0.1 mol L-1 aqueous sodium hydroxide. Paraformaldehyde, being insoluble in the sample solvent, does not present the inconvenience of other indicators that change the properties of the solvent due to composition changes. The titration can therefore be done effectively in the same medium as the standard potentiometric and visual titration methods. The results of the application of the method to both non-refined and refined oils are presented herein. The proposed method has advantages in relation to the potentiometric method in terms of speed and simplicity.

Formalin and paraformaldehyde as end-point indicators in catalytic thermometric titrimetry

The use of formalin solution as an end-point indicator in the titration of both acids and bases in aqueous solutions was investigated. In both instances, a lowering in temperature at the end-point, due to depolymerization of poly(oxymethylene glycols), was observed. Endothermic end-points were also obtained by using paraformaldehyde as an end-point indicator in titrations of acids in aqueous solutions. The use of paraformaldehyde in the titration of very weak acids and of some sparingly soluble acids solubilized in micellar suspensions of cationic detergents was also investigated.

Thermodynamic and kinetic implications involved in the titration of polyfunctional acids by catalytic thermometric titrimetry

The influence of the concentration of reactants on the results of titrations of salicylic acid in acetone with potassium and tetramethylammonium hydroxides in propan-2-ol were investigated. The titrations were performed by catalytic thermometric titrimetry using acetone as the end-point indicator and by potentiometric titrimetry. These and other results are discussed in terms of the equilibrium and kinetic aspects involved in the titrations of polyfunctional acids capable of forming intramolecular hydrogen bonds.

Titration of proteins in dimethyl sulphoxide–water mixtures

The acid–base behaviour of arginine, lysozyme and ovalbumin has been studied by potentiometric and catalytic thermometric titrimetry in a mixture of dimethyl sulphoxide–water, with acrylonitrile as the end-point indicator in the latter technique. It was observed that, with the exception of the SH groups, all the protonated groups, including the guanidine groups of lysozyme and ovalbumin, were titrated by catalytic thermometric titrimetry. By using potentiometric titrimetry, all the titratable groups of ovalbumin were determined, whereas the guanidine groups of lysozyme were not determined by this technique.

Use of cumene hydroperoxide as an end-point indicator in the titration of bases by catalytic thermometric titrimetry

The use of the decomposition reaction of cumene hydroperoxide for indication of the end-point of the titration of organic bases with perchloric acid was investigated. The rise in temperature at the end-point is of the order of 25 °C. Only strong bases can be determined when the titrand solvent is acetic acid-acetic anhydride (92 + 8 v/v), but even weak bases such as caffeine can be determined in 1,2-dichloroethane. Some titration curves resulting from titration of bases with boron trifluoride (a Lewis acid) are presented.

ChemInform Abstract: Applications of Catalytic Thermometric Titrimetry to Studies of Molecular Structure and Reactivity. Part 2. Condensation and Rearrangement Reactions of Carbonyl Compounds.

AbstractAliphatic and aromatic carbonyl compounds such as cyclobutanone, ‐pentanone, ‐hexanone, acetone, and benzil and some binary mixtures of these compounds are used as indicator reagents in the catalytic thermometric titration of benzoic acid with KOH in propanol.

Applications of catalytic thermometric titrimetry to studies of molecular structure and reactivity. Part 2. Condensation and rearrangement reactions of carbonyl compounds

Aliphatic and aromatic carbonyl compounds and some binary mixtures of these compounds are used as indicator reagents in the catalytic thermometric titration of benzoic acid with potassium hydroxide in propan-1-ol. Comparison of titration curves obtained in blank titrations and in titrations of benzoic acid are used to evaluate the relative reactivities of the carbonyl compounds when they undergo inter- and intra-molecular condensation and rearrangement reactions, and to investigate reaction processes with the binary mixtures. Consideration of the relative reactivities is used to establish relationships between reactivity and molecular environment of the carbonyl group.

Evaluation of the reactivity of vinyl monomers by catalytic thermometric titrimetry

Evaluation of the reactivity of vinyl monomers by catalytic thermometric titrimetry

Use of catalytic thermometric titrimetry to investigate the interaction of dipolar aprotic solvents with water

The interaction between water and the dipolar aprotic solvents dimethyl sulfoxide (Me/sub 2/SO), dimethylformamide (DMF), and hexamethylphosphoramide (HMPA) is investigated by a kinetic procedure in which catalytic thermometric titrimetry, with acrylonitrile as the thermometric indicator, is used to determine reaction rates. The interaction is measured by determining the influence of the solvents on the inhibiting effect of water on the base-catalyzed polymerization and cyanoethylation reactions occurring at the end point of the titration. The reactivity of the water is reduced by hydrogen bonding with the solvents, and discontinuities in the relationship between solvent-water molar ratio and end-point reaction rate confirm that association complexes are formed corresponding to molar ratios of 1:1 and 2:1, 1:1 and 2:1, and 1:1 for Me/sub 2/SO, DMF, and HMPA, respectively. 20 references, 4 figures.

Applications of kinetic methods in non-aqueous catalytic thermometric titrimetry. Part I. Evaluation of acetylation, α-methylstyrene and acrylonitrile indicator systems

Kinetic methods, based on the measurement of the rates of reaction of reagent systems originally developed as thermometric indicators, may be used as a method to determine perchloric acid, potassium hydroxide and quinoline in microgram amounts. The reaction rate is measured by the initial slope of the temperature-time graph recorded when the sample compound is added to the reagent mixture. Perchloric acid is determined using both acetylation and α-methylstyrene indicator systems, and potassium hydroxide is determined with the acrylonitrile reagent. Quinoline is determined on mixtures of quinoline and an excess of perchloric acid using the acetylation indicator reaction. The rate of the acrylonitrile reaction is influenced significantly by the presence of dimethyl sulphoxide, which is used to increase the sensitivity of the method. In the α-methylstyrene reaction, the induction time before the reaction commences is also used to measure the catalyst concentration.

Determination of metal salts in the presence of mineral acids by a combination of turbidimetric and catalytic thermometric titrimetry

Water-soluble salts of copper(II), nickel, chromium(III), iron(III), aluminium, cobalt, manganese(II), cadmium, zinc and lead(II) are determined titrimetrically in amounts down to 0.1 mequiv. in the presence and absence of hydrochloric, nitric and sulphuric acids. Ammonium salts are determined in the absence of free acids. When the mixture of metal salt and acid is titrated with aqueous potassium hydroxide, the end-point corresponding to the neutralisation of the free acid is determined by the onset of turbidity caused by precipitation of the hydroxide of the metal by the first excess of titrant. The titration is continued, and when all of the metal hydroxide is precipitated the final excess of titrant initiates the thermometric indicator reaction. The thermometric indicator, acetaldehyde, is diluted 1 + 1 with water to ensure solubility of the metal salts.

Assay of nitro and nitroso compounds by solution thermochemistry

Some nitro and nitroso compounds have been determined by direct reduction with Ti(III) chloride without the necessity for degassing the analyte solutions. Methods have been developed for the determination of some binary mixtures by both enthalpimetry and catalytic thermometric titrimetry. The accuracy at the 0.1 mMole level is±1%, and the time taken for a single titration is less than 2 minutes.

Application of the aldehyde reactions for the endpoint detection in the catalytic thermometric titration of acids

Exothermic reaction of formaldehyde polymerization in alcoholic medium which is catalyzed by diluted solutions of strong bases was used for catalytic thermometric endpoint indication in titrations of organic acids. The amounts of 7.80–23.10 mg of various organic acids were determined with a relative standard deviation less than 0.9%. The developed method was successfully applied also to determination of free acid content (formic acid) in aqueous solutions of formaldehyde of various manufacturers. Also investigated were the possibilities of the application of two new indicator reactions in catalytic thermometric titrimetry: the exothermic reactions of aldolic addition of both benzaldehyde and acetophenone, and benzaldehyde and methylethylketone, which are catalyzed in alcoholic medium by diluted solutions of strong bases. The influence of concentration of indicator reaction components, the solvent and the titrant, on the shape of catalytic thermometric curves was explored. The obtained results were compared to those of potentiometry and other standard methods.

Determination of the acidity of petroleum bitumens by catalytic thermometric titrimetry

The content of acids, including very weak acids, in straight-run and air-blown petroleum bitumens is determined by non-aqueous catalytic thermometric titrimetry. Titration values depend on the nature of the titrant and on the nature and amount of the sample solvent and thermometric indicator. Acrylonitrile is effective in low concentrations and is preferred to acetone as the indicator. With pyridine as the sample solvent, the measured acid contents are similar to those obtained by non-aqueous potentiometric titration. The thermometric method is more convenient.

Applications of catalytic thermometric titrimetry to studies of molecular structure and reactivity. Part 1. Organic hydroxy groups

Solutions of organic hydroxy compounds in acetic anhydride are used as indicator reagents in the catalytic thermometric titration of the weak base, quinoline, and the very weak base, caffeine, with perchloric acid in acetic acid. Comparisons of the titration curves are used to evaluate the relative reactivities of the hydroxy reagents. Consideration of these relative reactivities for hydroxy compounds of similar structure is used to establish relationships between reactivity and molecular environment of the hydroxy group.

The analysis of phenol‐, resorcinol‐ and phenol/resorcinol‐formaldehyde resins by catalytic thermometric titrimetry. Part II. Resoles

AbstractCatalytic thermometric titration is used for the determination of the phenol and resorcinol components of resins formed by the sodium hydroxide‐ and ammonia‐catalysed condensations of phenol, resorcinol and mixtures of phenol and resorcinol, with formaldehyde.

The determination of weak acids in aqueous solution by catalytic thermometric titrimetry

The determination of weak acids in aqueous solution by catalytic thermometric titrimetry

The analysis of phenol‐, resorcinol‐ and phenol/resorcinol‐formaldehyde resins by catalytic thermometric titrimetry. Part I. Novolacs

AbstractNon‐aqueous catalytic thermometric titration is used for the determination of the phenol and resorcinol components of resins formed by the acid‐catalysed condensation of phenol, resorcinol and mixtures of phenol and resorcinol, with formaldehyde.

Ionic polymerisation as a means of end-point indication in non-aqueous thermometric titrimetry. Part VI. The determination of thiols

Alkyl and aryl thiols have been determined in the presence of carboxylic acids and phenols by means of acid-base catalytic thermometric titrimetry. Two titrations are carried out, with acrylonitrile and acetone as the end-point indicators. With the former indicator, thiol groups are not determined, so that the difference between the titration values obtained by using the two methods of end-point indication is a measure of the thiol content.