Determination of tetraphenylborate by two-phase titration with tetraphenylphosphonium salt

A visual indicator method has been developed for the titration of tetraphenylborate (TPB) with a 5 × 10^?5, M tetraphenylphosphonium (TPP) solution. A hydrophobic dye, tetrabromophenolphthalein ethyl ester (TBPE), is used as an indicator in the presence of 1,2-dichloroethane. The organic phase changes from yellow to blue at the endpoint. This method was applied to the determination of solubility product of TPP perchlorate. The extract of ephedrine, homatropine, perchlorate, or thiocyanate with TPB or TPP was titrated.     

Decimilligram-scale determination of sulfur in organic compounds

A simple and rapid method for the decimilligram-scale determination of sulfur in organic compounds is described. The procedure utilizes the Schöniger flask method for the combustion and the sulfate-ion titration, with 0.01 M barium perchlorate solution and dimethylsulfonazo III as indicator. The results obtained are exact and precise.     

Lower limits of the potentiometric microtitration of chloride with silver ions

The lower levels of the potentiometric titration of chloride with silver ions were investigated. The titrant was 0.001 N acetonic silver perchlorate. The titration media were acetone and acetic anhydride:acetone (4:1). A silver sulfide ion-selective indicator electrode and a double-junction reference electrode were use to monitor emf's. This titration is limited only by the trace amounts of chloride in the reagents used. Satisfactory results and well-defined titration curves were obtained down to 7 μg of chloride per 50 ml of solution (0.2 μmol; 4 × 10^?6N).A small polarization current can be used to enhance the potentiometric breaks of this titration. In an 80% methanolic medium with 0.001 N aqueous silver nitrate and a polarization current of ?0.4 μA, the lower practical limit of this titration was near 22.3 μg of chloride (1.26 × 10^?5N).     

Complexometric catalytic titrations using the indicator reaction periodate-triethanolamine

The possibility of applying a new indicator reaction, i.e., periodate-triethanolamine, as the indicator in titrations of ethylenediamine-N,N,N′,N′-tetracetic acid (EDTA), 1,2-diaminocyclohexanetetraacetic acid (DCTA), and diethylenetriaminepentaacetic acid (DTPA) with standard manganese(II) sulfate solution (phosphate buffer pH 6.84) has been investigated. The titration course was followed potentiometrically using a perchlorate ion-selective electrode. The optimum conditions for determinations in relation to concentration of the indicator reaction components have been established. Furthermore, the influence of some ions on the possibility of EDTA determination was considered and maximally tolerable concentrations under these conditions were established. The amounts of 0.170–18.00 mg of EDTA, 0.150–16.00 mg of DCTA, and 0.180–19.00 mg of DTPA were determined with a maximal relative standard deviation less than 1.0%. Results are in good agreement with those of comparable methods. Finally, the experimental catalytic titration curves obtained in this way are compared to the simulated ones.     

Rationally designed chromogenic chemosensor that detects cysteine in aqueous solution with remarkable selectivity

A sensing ensemble for cysteine was assembled conveniently by simply mixing N,N,N′,N′-tetra-(2-pyridylmethyl)-p-xylylenediamine (TPXD), cadmium perchlorate, and pyrocatechol violet in an 1:2:1 molar ratio in water of neutral pH. In the ensemble, [Cd₂(TPXD)]⁴⁺ formed from TPXD and cadmium perchlorate serves as the receptor, and pyrocatechol violet functions as the indicator in sensing the analyte. The detection can be made either spectroscopically from the decrease of the UV-visible absorbance at 665 nm or visually from the color change to yellow upon addition of an aqueous solution of the analyte to the solution of the ensemble. The association constant (K_ass) for the binding of the indicator to the receptor was determined with an isothermal titration calorimeter to be (2.77±0.98)×10⁵ M⁻¹ and that for the binding of cysteine to the receptor was obtained to have (1.62±0.97)×10⁷ M⁻¹ by the non-linear regression analysis of the titration curve obtained by titration of the solution of the ensemble with cysteine solution. The chemosensor showed excellent selectivity for cysteine over other amino acids including homocysteine.     

Lower limits of the potentiometric titration of perchlorate using a perchlorate ion-selective electrode

Three titrants (tetraphenylarsonium chloride, tetraphenylphosphonium chloride, and tetra-n-pentylammonium bromide) were evaluated for the potentiometric determination of perchlorate. The emf levels were monitored with a perchlorate ion-selective indicator electrode and a double-junction reference electrode. The tetraphenylonium salts were equivalent, yielding the same precision and magnitude of potentiometric breaks. Considerably smaller breaks were obtained with tetra-n-pentylammonium bromide, which, therefore, is not recommended as titrant.The lower limits for the potentiometric titration of perchlorate at ambient temperature were extended to ~0.09 mmol per 50 ml (1.7 × 10^?3N) from the previous 0.25 mmol per 50 ml. If Gran plots are used, they can be further extended to ~0.01 mmol per 50 ml (2.1 × 10^?4N).     

Development of a method for estimating an accurate equivalence point in nickel titration of cyanide ions

In a nickel titration of cyanide ions using murexide as indicator, an accurate equivalence point was determined by a non-linear least-squares curve-fitting for a titration curve. This method was developed to establish a standard solution for cyanide ions. In a curve-fitting procedure, a theoretical titration curve was calculated, assuming that nickel ion formed only a 1:4 Ni²⁺:CN⁻ complex with cyanide ions and formed only a 1:1 complex with murexide. Results of the curve-fitting were reasonable at any pH and any indicator concentration studied. The combined standard uncertainty for a concentration of a 1000 mg kg⁻¹ cyanide solution by this method was 0.079%.     

Statistical Analysis of Differential Potentiometric Precipitation Titration Data for a Mixture of Three Heterovalent Ions Using Linear Characteristics

A computer-based method is proposed for data processing in the successive potentiometric precipitation titration of a three-component mixture of differently charged ions. It is based on a piecewise transformation of the titration curve into linear regression characteristics, the parameters of which determine the successive equivalence points and the solubility products of the precipitates formed in the course of titration to the accuracy of least-squares estimates. To implement the calculation algorithm, a DIFTITR2 program written in Turbo Pascal was developed. The method was tested on the titration of an artificial solution containing a mixture of Cd(II), Hg(II), and Te(IV) with diethyldithiocarbamate, using a chalcogenide Cd-selective or a glassy-carbon indicator electrode, and was used for the analysis of the main components in a semiconductor material, namely, a solid solution of mercury and cadmium tellurides. For concentrations of test ions in the model solution from 7.5 × 10^–3 to 3 × 10^–4 M, the RSD value varies from 0.01 to 0.3; the determination error does not exceed 6%. The RSD value for the semiconductor alloy lies in the range of from 0.002 to 0.01.     

Determination of sulfur dioxide in air

The determination of sulfur dioxide in air is based on a preliminary purification with a cellulose filter and 80% isopropanol and absorption of sulfur dioxide by means of two midget impingers in 0.3 N hydrogen peroxide. The formed sulfate is titrated in an aliquot with 0.005 M barium perchlorate employing Chlorophosphonazo III (CPA) as an indicator. The method is suitable for 0.3–19.0 mg of sulfur dioxide per 50 liters of air. The standard deviation of the titration is ±0.02 ml per consumption of 5.00 ml and is four times smaller than that of the Thorin method.     

Rapid titrimetric determination of microgram amounts of fluoride ion with spadns -thorium lake

A rapid titrimetric method has been developed for the determination of microgram amounts of fluoride ion in the range from Img-Ioomg, in 50 ml final volume. It involves the adjustment of pH, addition of 1 ml of 0.02% SPADNS indicator, dilution to volume and titration with standard 0.004M Th(NO₃)₄ until the colour obtained matches a blank containing the buffered solution of the indicator with a. trace of thorium nitrate solution. Interference by various ions was also studied. The method described for the determination of fluoride ion is very rapid and the colour change at the end point being sharp, the detection of the end point is very easy. The method is applicable to pure solutions of fluondes.     

Copper (II) as an Amperometric Indicator: Determination of Thorium

Abstract

It has been demonstrated that copper (II) is an attractive amperometric indicator for the titration of small amounts of thorium in solution. EDTA was used as the titrant. Best results are obtained in the titration when the mole ratio of thorium to copper is high. The method should be applicable to several other metal ions that form more stable EDTA complexes than does copper.     

Coulometric titration of bases in acetic acid and acetonitrile media

The working conditions and the results for coulometric titration of milligram amounts of some bases in 0.1M sodium perchlorate in a mixture of acetic acid and acetic anhydride (1:6), are given. Determinations were made both by coulometric back-titration or direct titration at the platinum anode. Back-titration was done in the catholyte, by coulometric titration of the excess of added perchloric acid. The titration end-point was detected photometrically with Crystal Violet as indicator. The direct titration of bases was done at the platinum anode, in the same electrolyte, to which hydroquinone was added as anode depolarizer and as the source of hydrogen ions, Malachite Green being used as indicator. Similarly, bases can be determined in acetonitrile if sodium perchlorate, hydroquinone and Malachite Green are added to the solvent. Errors are below 1 %, and the precision is satisfactory.     

Graphite-silver diethyldithiocarbamate as a new potentiometric sensor for titration of some metals,halides, thiols,and sulfonamides

A new simple potentiometric sensor based on the precipitation of AgDDC within a graphite rod is described. The electrode is sensitive for both DDC and silver ions down to 10^?5M and can be used as an indicator electrode for complexometric titration of metallic ions with NaDDC and argentimetric titration of some organic and inorganic compounds. Accurate results are obtained for microdetermination of some metal ions singly or simultaneously (in binary and tertiary mixtures and alloys) and thiols, sulfonamides, and halides in organic compounds.     

Isothermal titration calorimetric studies of the acid-base properties of poly(N-isopropylacrylamide-co-4-vinylpyridine) cationic polyelectrolyte colloidal microgels

Isothermal titration calorimetry (ITC) and potentiometric titration were used to study the protonation properties of the 4-vinylpyridine (4-VP) moiety in cationic poly(N-isopropylacrylamide-co-4-vinylpyridine) colloidal microgels [poly(NIPAM-co-4-VP)]. Calorimetric pH titrations were performed using microgels of different 4-VP content and the influence of ionic strength and counter ions have been examined. The calorimetric titration output consists of several thermal contributions reflecting the complex nature of the interactions in the aqueous microgel dispersions. In contrast to the potentiometric results, the calorimetric titration data could not be completely described by a theoretical model solely taking into account protonation equilibria. Deviations from the proposed model correlate with swelling or shrinking of the gel particles. The calorimetric results also reveal a pronounced counter-ion effect of perchlorate compared to chloride ions. In the presence of perchlorate ions, small secondary thermal effects accompany protonation of the 4-VP moiety due, in part, to kinetically limited conformational changes in the co-polymer microgel.     

Determination of sulfate in waters

Determination of sulfate in industrial waters is performed by shaking with Dowex 50-X8 resin (removing of metal ion interferences) and titration of aqueous acetone ($\text{1}\text{1}\text{,}\text{v}\text{v}$) solution with barium perchlorate employing Dimethylsulfonazo III as indicator. Only phosphate and arsenate interfere.     

Process monitored spectrophotometric titration coupled with chemometrics for simultaneous determination of mixtures of weak acids

A new spectrophotometric titration method coupled with chemometrics for the simultaneous determination of mixtures of weak acids has been developed. In this method, the titrant is a mixture of sodium hydroxide and an acid-base indicator, and the indicator is used to monitor the titration process. In a process of titration, both the added volume of titrant and the solution acidity at each titration point can be obtained simultaneously from an absorption spectrum by least square algorithm, and then the concentration of each component in the mixture can be obtained from the titration curves by principal component regression. The method only needs the information of absorbance spectra to obtain the analytical results, and is free of volumetric measurements. The analyses are independent of titration end point and do not need the accurate values of dissociation constants of the indicator and the acids. The method has been applied to the simultaneous determination of the mixtures of benzoic acid and salicylic acid, and the mixtures of phenol, o-chlorophenol and p-chlorophenol with satisfactory results.     

Spectrophotometric titration of cryptands and compleximetric titration of barium with cryptand (2.2.2)

A spectrophotometric titration of cryptands (2.2.1), (2.2.2), (2_B.2.2) and (2_B.2_B.2) in aqueous medium is described. Titration of the cryptands with standard lead(II) perchlorate allows these cryptands to be quantified down to 1.0 × 10^?5 M. The compleximetric titration of barium(II) with cryptand (2.2.2) using metalphthalein indicator is described and compared with a similar method with EDTA as titrant.     

Simultaneous determination of microgram amounts of chlorine or bromine or iodine and sulfur in organic compounds

A general method for the simultaneous and rapid determination of microgram amounts of chlorine or bromine or iodine and sulfur in organic compounds is described.The procedure is based on the combustion of the sample, containing approximately 0.005 meq of Cl or Br or I and 0.005 meq of S. by the Schöniger flask technique, using potassium hydroxide and hydrazine hydrate as absorption solution. The excess of hydrazine is eliminated with hydrogen peroxide after combustion.This method allows complete reduction of halogens to halides and oxidation of sulfur to sulfate.The halide ions are titrated with mercuric perchlorate and diphenylcarbazone as indicator; the sulfate ions with barium perchlorate and dimethylsulfonazo(III) as indicator.The results obtained are in good agreement with calculated values.     

Mikroanalytische Bestimmung von Chlor (Brom) und Schwefel in organischen Verbindungen in einer Einwaage

Zusammenfassung Bei der maßanalytischen Bestimmung von Chlorid(Bromid)ionen wird ein exakter und farbkräftiger Umschlag erzielt, wenn mit isopropanolisoher Silberperchloratlösung in mindestens 80%igem Isopropanol titriert und Dichlorfluoreszein als Neutralisations- und Adsorptionsindikator angewendet wird. Eine vorhergehende Sulfattitration nachH. Wagner stört unter diesen Bedingungen nicht, so daß Chlor (Brom) und Schwefel in einer Einwaage schnell und sicher bestimmt werden können.

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Summary A precise and color-intensive change is obtained in the titrimetric determination of chloride (bromide) ions, if the titration is made with isopropanolic silver perchlorate solution in not less than 80% isopropanol, and if dichlorofluorescein is used as neutralization- and adsorption indicator. Under these conditions, no interference is encountered because of a preliminary sulfate titration afterH. Wagner, so that chlorine (bromine) and sulfur can be determined quickly and accurately in a single sample.

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Résumé Lors du titrage des ions chlorure ou bromure on obtient un virage exact et très coloré en effectuant le dosage avec une solution isopropanolique de perchlorate d'argent titrant au moins 80% en isopropanol en présence de dichlorofluorescéine comme indicateur de neutralisation et d'adsorption. Un titrage préalable des sulfates d'aprèsH. Wagner⁵ ne gêne pas, dans ces conditions, de sorte qu'il est possible de déterminer rapidement et sûrement le chlore (le brome) et le soufre sur un seul prélèvement analytique.

     

Non-aqueous titration of quinine and quinidine sulphates by use of barium perchlorate

A simple non-aqueous titration method has been devised for determining the sulphates of quinine and quinidine. The sulphate is precipitated by addition of excess of barium perchlorate solution in acetic and the liberated alkaloid is then titrated in 1:2 anhydrous acetic-dioxan mixture, with an acetic acid solution of perchloric acid. The end-point is determined either visually with Crystal Violet as indicator or potentiometrically with a glass-Ag/AgCl combination electrode. The method is accurate, precise and suitable for routine analysis of pure materials and tablets.