Acid-base titrations by stepwise addition of equal volumes of titrant with special reference to automatic titrations-IV Photometric titration of an acid

In Part I of this series, evaluation methods for potentiometric titrations of acids performed by stepwise addition of titrant were introduced. These methods are non-approximative and may therefore in principle be applied to titrations of acids of any strength. This paper demonstrates that photometric titrations performed by stepwise addition of titrant may also be evaluated by the proposed methods. The photometric method is compared with the potentiometric method of monitoring the course of a titration.     

Determination of 2-hydroxy-5-methyl-4′-methoxy chalkone oxime (HMMCO) and substituted oximes by enthalpimetric and potentiometric titrations

Enthalpimetric and potentiometric titrations of 2-hydroxy-5-methyl-4′-methoxy chalkone oxime (HMMCO), 2-hydroxy-5-chloro-4′-methoxy chalkone oxime (HCMCO), and 2-hydroxy-3-bromo-5-methyl-4′-methoxy chalkone oxime (HBMMCO) were carried in acetone medium using tetra-n-butyl ammonium hydroxide, potassium hydroxide in isopropyl alcohol, and potassium tertiary butoxide in tertiary butyl alcohol, as titrants. Alcoholic KOH was found to be the most suitable titrant. Enthalpimetric titrations could be used for 1–8 mg of oximes where as potentiometric titrations gave accurate results for 1–20 mg.     

Bromamine-B as a new oxidimetric titrant

A new oxidimetric titrant, bromamine-B (sodium salt of N-bromobenzenesulphonamide) is introduced for use in aqueous medium. Direct potentiometric and visual end-point titrations and back-titration procedures have been developed for the determination of typical reductants.     

Dichloramine-T as a new oxidimetric titrant in non-aqueous and partially aqueous media

A new oxidimetric titrant, dichloramine-T, is proposed for redox titrations in glacial acetic acid medium. The general analytical conditions for using this oxidant and the procedures for potentiometric determination of ascorbic acid, iodide, arsenic(III) and iron(II) are described.     

In Process Citation

A first attempt to apply inorganic membranes made from parchment paper impregnated with alkaline earth precipitates, as indicating electrodes for potentiometric acid-base titrations in nonaqueous media, is presented. Mixtures of acids can be titrated and the course of the titration is a function of the nature of the solvent and the titrant.     

New redox titrants in non-aqueous or partially aqueous media--VI: potentiometric determinations using dibromamine-T and some further applications of dichloramine-T

A new redox titrant, Dibromamine-T (N,N'-dibromo-p-toluenesulphonamide) is introduced for use in acetic acid media. Potentiometric titrations of Sb(III), As(III), Tl(I), Fe(II), ferrocyanide, iodide, ascorbic acid, hydroquinone, hydrazine, aniline, phenol and oxine are described. Direct potentiometric titrations of oxinates of Mn, Fe, Co, Ni, Cu and Zn with Dibromamine-T as well as with Dichloramine-T are also described.     

Controlled dynamic titrator

The controlled dynamic titrator described operates with constant titrant flow and time-proportional sample flow; sample and titrant are mixed in a microcell and the equivalence point is reached when the products of the normalities and flow rates of the titrant and the sample are equal. Titration times are measured and printed out. The concentration of the sample is inversely proportional to the titration time. The automatic titrator is discontinuous and suitable for on-line and off-line use. The cycle time of the motor-driven programmer is 2 min. Flow-through detectors for potentiometric, photometric or voltammetric indication can be used for a selection of acid—base and redox titrations. With this equipment, titration of large series of liquid samples with similar contents is simple.     

Berechnung des Endpunktes potentiometrischer Titrationen mit programmierbaren Tischrechnern

Zusammenfassung Die verschiedenen in der Literatur beschriebenen Näherungsverfahren für die Endpunktsberechnung potentiometrischer Titrationen aus den Potentialdifferenzen bei gleichen Reagensvolumenschritten werden gegenübergestellt und Programme für die Diehl Combitron S beschrieben, die auch auf andere programmierbare Tischrechner übertragen werden können.

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Computation of the end-point of potentiometric titrations with programmable minicomputers

Some possibilities are described for computing the end-point of potentiometric titrations from the differences of electrode potentials at equal steps of titrant volumes. For different methods from the literature programs for the Diehl-Combitron S are described, which are also useful for programming other minicomputers.

     

Titrations using an apparatus for recording the antilogarithm of pH or pM

A titration apparatus plotting either the concentration of sample ion or the concentration of titrant ion has been tested. An antilog apparatus, converting measured e.m.f. values into concentrations is connected to ordinary titration equipment. The instrument has been tested by means of acid—base titrations (titrations of mixtures of weak acids and of a weak and a strong acid), precipitation titrations (determination of the chloride concentration in tap-water, titration of mixtures of halides), titrations with ion-selective electrodes (determination of the fluoride content of toothpaste) and complexometric titrations (determination of copper with EDTA, using mercuric ion as indicator ion and amalgamated silver rod as indicator electrode, or using a copper-selective indicator electrode). The method considerably simplifies the evaluation of the results as compared to conventional potentiometric titrations.     

Optimization of the automatic microtitration of chlorides,bromides and iodides

Summary The most favourable conditions for performing the potentiometric micro-scale determination of chlorides, bromides and iodides by their automatic titration with silver nitrate have been investigated. For this purpose, an automatic device has been considered which is able to perform the titrant addition, either for preselected time intervals, or by adjusting them automatically so that the change of potential with time reaches a preselected value.The results obtained indicate that rapid (about two minutes) and accurate titrations can be performed for chlorides with almost all of the parameters chosen, while results affected by a large positive error are obtained for bromides and iodides when the operation modes adopted imply too frequent titrant additions.The weighed samples contain 1.5 to 4 mg halide.     

高精度散射光度滴定法测定诺氟沙星的含量

用四苯硼钠标准溶液作滴定剂,采用高精度散射光度滴定法测定了诺氟沙星的含量,并将测定结果与非水滴定法、非水电位滴定法和高效液相色谱法的测定结果进行比较。结果表明：用本方法测定诺氟沙星的含量具有较高的准确度、精密度和良好的线性,且不受其降解产物的干扰。     

Potentiometric and visual titrations with bromamine-B

Bromamine-B is proposed as an oxidimetric titrant for potentiometric and visual end-point titrations of arsenic(II), hexacyanoferrate(II), antimony(III), hydroquinone, semicarbazide hydrochloride, isonicotinic acid hydrazide, hydrazine sulphate, ascorbic acid, phenylhydrazine hydrochloride and metol. Quinoline Yellow, naphthidine, dimethylnaphthidinedisulphonic acid, o-dianisidine, diphenylbenzidine, Variamine Blue, alpha-naphthoflavone, Amaranth, Methyl Orange and Methyl Red are proposed as indicators in macro and micro titrations of the reductants with bromamine-B. The transition potentials of Quinoline Yellow, naphthidine, dimethylnaphthidinedisulphonic acid, and o-dianisidine in the titration of ascorbic acid are reported. Arsenic(III) and hexacyanoferrate(II) are suggested for the standardization of bromamine-B solutions.     

18-Crown-6-potassium Ferricyanide Complex as a Potentiometric Titrant

Abstract

An oxidimetric titrant, 18-Crown-6-potassium ferricyanide complex, has been prepared in acetonitrile. This reagent is proposed for redox titrations in aqueous - acetonitrile media of some reductant compounds. The general analytical conditions for using this complex and the procedures for potentiometric determinations of oxalate, arsenic (III), thiocyanate, nitrite, sulfite, thiosulphate and iodide ions, as well as hydrazine sulphate and hydrogen peroxide are presented.     

Determination of fiber charge components of Lo-solids unbleached kraft pulps

Four different titration methods for measurement of fiber charge were used in this study. Each method gave different fiber charge values depending on the acidity of the end point and the interaction between the fiber chemical components and the titrant. Also, the interactions between the ionizable groups on the fiber had significant effects on the interpretation of these results. The conductometric titrations showed trends similar to the results obtained from the potentiometric titration. The conductometric titrations with NaOH produced higher fiber charge values, higher than the titrations with NaHCO(3). The differences between the results obtained from the potentiometric and polyelectrolyte titrations, which were associated with the dissolved fiber components during the delignification, were linearly related to the Kappa number of pulps. The positive intercept of this linear relationship indicated that the kraft pulping process not only removed the ionizable groups associated with the dissolved components, but at the same time provided conditions to form new ionizable groups in the fibers. The polyelectrolyte titration results indicated that the lignin content in the fibers did not affect the fiber surface charge. Data extracted from the FTIR spectra of protonated fibers were highly correlated with the fiber charge values obtained from the conductometric titration with NaOH.     

Titrations of weak acids in 1,1,3,3-tetramethylguanidine

The use of 1,1,3,3-tetramethylguamdine (TMG) as a medium for the titrations of weak acids has been investigated. The hydrogen electrode behaves reversibly in this solvent and can serve as an indicator electrode in titration reactions. The titrant was a o.1 M solution of tetrabutylammonium hydroxide in a 90-10% mixture of TMG and methanol. A hydrogen electrode dipping into a TMG solution saturated with benzoic acid served as reference electrode. Potentiometric titrations of a number of weak acids gave results accurate to at least ±0.5%. It was found that in most cases curcumin could be used as an end-point indicator with an accuracy comparable to that of the potentiometric titration.     

Determination of stability constants of complexes of MiKjHkL type in concentrated solutions of mixed salts

This paper suggests a non-conventional approach towards the correct determination of stability constants K_ijk of mixed complexes from the results of potentiometric titrations. The method is based on inaccurate (in principle) results of titrations made in isomolar titrand–titrant systems. The data thus obtained are validated on the basis of relationships between log K_ijk and relative error (%e) of the determination of an analyte concentration. Accurate values for K_ijk are calculated for the set (ijk) of possible complexes. The accuracy depends on the degree of linearity between the variables considered. The model obtained was thoroughly tested on the system containing malonic acid together with sodium and potassium nitrates.     

Electrolytically generated silver(II) as a coulometric titrant

The use of electrolytically generated silver(II) as a coulometric titrant has been studied. Difficulties arising from the current efficiency for generation of silver (II) at a platinum or gold electrode and from the reduction of silver(II) by water, have been overcome. The precautions necessary for accurate titrations of oxalic acid, cerium(III), arsenic(III) and vanadium(IV) by amperometric or potentiometric methods are detailed. Manganese and chromium could not be determined directly. Substances which reduce nitric acid could be determined if care was taken.     

NABTIT-a computer program for non-aqueous acid-base titration

A program NABTIT written in BASIC has been developed for the treatment of data (ml/mV) obtained from potentiometric acid-base titrations in non-aqueous solvents. No preliminary information on equilibrium constants is required for the input. The treatment of the data is based on known equations and uses least-squares procedures. The essence of the method is to determine the equivalence volume (V(e)) accurately, and to use the data acquired by adding titrant after V(e) for the pH*-calibration of the non-aqueous potentiometric cell. As a by-product or the calculations, the pK* value of the substance titrated is also obtained, and in some cases the autoprotolysis constant of the medium (pK*(s)). Good agreement between experiment and theory was found in the treatment of data obtained for water and methanol-water mixtures.     

An evaluation of some simple sulfonic acids as nonaqueous titrants

The simple aliphatic and aromatic sulfonic acids show evidence of possibilities as new titrants in a glacial acetic acid medium. Excellent precision is obtained in potentiometric titrations with both ethane- and methane sulfonic acids with a standard deviation of 0.2%. Benzenemonosulfonic and naphthalenesulfonic acids both give an average precision of 0.4%. In visual titrations with with crystal violet indicator, the color changes at the end-point are very sharp. The chief advantage of these acids as titrants lies in the fact that they dissolve readily in glacial acetic acid and can be titrated to give reproducible results with the glass-calomel electrode system. None of the sulfonic acids tested was as strong a titrant as perchloric acid, but, unlike perchloric acid, they did not form precipitates or gels in the titration with potassium acid phthalate.     

Ion-selective electrodes in titrations involving azo-coupling reactions: Part 2. Titrations with diazonium salts derived from 1-aminonaphthalenes and 1-amino-9,10-anthraquinone

Lipophilic arenediazonium salts dreived from 1-aminonaphthalene, 1-amino-4-bromonaphthalene, 1-amino-4-nitronaphthalene and 1-amino-9,10-anthraquinone were tested as titrants for determination of aromatic hydroxy compounds, amines, and compounds containing active methylene groups, usually at the 10^?2 M level. The potentiometric titrations were monitored with indicator electrodes selective for organic cations which were based on PVC membranes plasticized with 2-nitrophenyl alkyl ethers (where alkyl is n-octyl or 2-ethylhexyl). Titrations of 11 compounds ranging from 1,2-diaminotoluene to 1-phenyl-3-methyl-5-pyrazolone were examined; 4-bromo-1-naphthalenediazonium chloride seemed to be the most widely applicable titrant.