High precision titrimetry: An examination of the attainable precision

A re-examination and critical assessment of the mechanical precision of titrimetric processes, with particular reference to the drainage errors of burettes, has been made and some manipulative improvements suggested.The piputte-dilution method offers a useful improvement in the precision of volumetric methods, further increase in mechnical precision affords little or no improvement in accuracy of determination.     

Ammonium 2-(2'-lepidylazo)-1-naphthol-4-sulphonate as indicator in mercurimetric determination of halides

The use of ammonium 2-(2'-lepidylazo)-1-naphthol-4-sulphonate as indicator in titrimetric estimation of chloride, bromide and iodide with mercury(II) has been examined. The precision, accuracy and applicability of the procedures have been evaluated.     

Titrimetric estimation of phosphate, molybdate, tungstate and sulphate with lead nitrate solution, using 1,2-naphthoquinone-2-semicarbazone-4-sulphonic acid (NQS-4S) and 1,2-naphthoquinone-2-thiosemicarbazone-4-sulphonic acid (NQTS-4S) as visual indicators

The use of 1,2-naphthoquinone-2-semicarbazone-4-sulphonic acid and 1,2-naphtho-quinone-2-thiosemicarbazone-4-sulphoic acid as indicators in the titrimetric estimation of phosphate, molybdate, tungstate and sulphate with lead has been examined. The precision, accuracy and applicability of the methods have been evaluated.     

A coulometric iodimetric procedure for measuring the purity of lewisite

A new analytical method for the determination of the purity of CASARM Lewisite samples (Chemical Agent Standard Analytical Reference Materials) has been developed and tested. The method essentially replaces the volumetric iodimetric procedures currently in use with the in-situ electrochemical generation of iodine. Tests on both arsenious acid and Lewisite/CVAA solutions show that the method is capable of achieving high accuracy and precision. Sample preparation and analysis times are considerably less than the current titrimetric method. The coulometric iodimetric method has been shown capable of determining not only total organic trivalent arsenic, but also total trivalent arsenic merely by adjusting the pH. Organic arsenic is determined at pH 4, and total trivalent arsenic at pH 8.     

Oxidation of plutonium by cobalt(III) green

A stable green solution of tricarbonatocobaltate(III) has been prepared and used for the redox titrimetric determination of plutonium in HNO₃ medium. Quantitative oxidation could be achieved and excess oxidant could be destroyed by NaNO₂. Pu(VI) was deter-ined by adding known excess of Fe(II) and carrying out potentiometric titration. The precision at the level of 0.5–5.0 mg was 2% RSD.     

The initiation of polymerization by organometallic compounds—IV. Initiator efficiency in polymerization of acrylonitrile by tetrakis(dimethylamido)titanium(JV)

A titrimetric method has been developed for following the removal of titanium-dimethylamine bonds during the polymerization of acrylonitrile by tetrakis(dimethylamido)titanium(IV) (T₄). The kinetics of the reaction of T₄ with monomer can be interpreted in terms of a sequence of insertion reactions in which dimethylamino ligands are successively removed from titanium. The calibration of a GPC instrument for measurement of the molecular weights of polyacrylonitrile is discussed. The results of initiator consumption and polymer molecular weight measurements are combined to allow the efficiency of initiation by T₄ to be assessed. Over the whole conversion range, titanium-dimethylamine bonds are broken in about 50 per cent excess over those used for polymerization. However, at high conversions more than one polymer chain is produced per titanium atom reacted.     

High-precision gravimetric coulometry using the silver-perchloric acid coulometer: Titration of arsenious oxide with electrogenerated iodine

High-precision gravimetric coulometry with a silver-perchloric acid coulometer is evaluated as an alternative to the conventional titrimetric method. The loss of weight (caused by electrolytic dissolution) of a highly pure silver anode in series with the cathode of a conventional constant-current titration system is measured and related to the number of equivalents of substance titrated. The precision of the method is determined by titrations of the Standard Reference Material 83C arsenious oxide (99.99% pure) with electrogenerated iodine, using biamperometric end-point detection. Depending on the size of the sample, an ultimate precision of 25 ppm is obtained. The assay for 0.5-g samples of the SRM material is 99.993(9) +/- 0.002(5)% purity.     

Rapid method of uranium determination in solutions based on X-ray fluorescence and absorption

A method of uranium determination in organic and aqueous solutions has been developed, based on fluorescence L X-ray excitation with a¹⁰⁹Cd source of several mCi activity and counting the excited L_α lines with a proportional counter. To eliminate uranium X-ray absorption by the accompanying elements the intensity of the source radiation (Ag K) transmitted through the analysed solution is measured. The ratio of these two intensities is independent of other elements present in the solution over a very broad range of concentration. The analysis time does not exceed 5 minutes. The precision and accuracy of this method in the range 0.5 to 100 g U/1 are comparable to those of the classical titrimetric method.     

Comparison of γ activation and vacuum distillation for determination of oxygen in sodium

A γ photon activation technique has been applied to the determination of oxygen in sodium and the results obtained compared with those using vacuum distillation. Care has been taken to ensure that sampling errors are minimised and a specially designed sampling, storage and irradiation container for γ extraction has been developed. Initial results show favourable agreement between the techniques but the precision of γ activation results requires to be improved.     

A highly accurate and precise method for the assay of chromium metal and chromium(III) oxide

A method capable of a precision of 3 to 5 parts in ten thousand has been developed for the routine assay of high purity chromium metal and chromium trioxide. Use has been made of the favourable gravimetric factor of ferrous ammonium sulfate and of an amperometric end-point. Comparison with the arsenic trioxide method was made.     

Vollautomatische titrimetrische Einzelanalyse in der Praxis

Zusammenfassung Voraussetzungen einer effektiven Automation der individuellen titrimetrischen Analyse werden dargestellt. Ein nach diesen Gesichtspunkten entwickeltes Gerät wird beschrieben und seine Anwendung in den Gebieten der Farbstoffe, Agrochemikalien, Additiven und Pharmaka aufgezeigt.

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Fully automated titrimetric individual analysis in practice

Summary Criteria for effective automation of individual titrimetric analyses are presented. Based on these, an automatic titration system has been developed which is described. Its performance and its applicability in the field of dyestuffs, agrochemicals, additives and pharmaceuticals has been investigated.

     

Indirect determination of isocyanates by gas chromatography

A gas chromatographic method was developed to determine the purity of synthesized isocyanate monomers, specifically isocyanatoacrylates, and to determine the isocyanate content of synthesized polymers and prepolymers. The method is a modification of an ASTM procedure in which an isocyanate is allowed to react with excess di-n-butylamine. In the ASTM method, the amount of isocyanate present is calculated indirectly from the amount of unreacted di-n-butylamine, determined by back titration with standard hydrochloric acid. Determination of the excess di-n-butylamine by the gas chromatographic method developed has the advantages of providing better precision and requiring less sample than the titrimetric method. The two methods were compared using phenyl isocyanate as a model test compound. A synthesized monomer, methyl alpha-isocyanatoacrylate, was also analyzed, for comparison by both methods.     

Derivation of continuous molecular weight distributions from the generating function

A method described in the statistical literature for the numerical inversion of Laplace Transforms of real functions has been adapted for the derivation of molecular weight distributions from calculations of the generating function for a polymeric system. It has been shown that a third-order refinement is sufficiently accurate for molecular weight distributors broader than 4.0. This allows the calculations to be carried out with a precision of 16 decimal digits which is commonly used in Fortran. Where higher precision is available, the treatment is applicable to narrower MWDs.     

Titrimetric determination of vanadium(IV) with cerium (IV)sulphate at room temperature using ferroin as indicator

A procedure has been developed for the visual titrimetric determination of vanadium(IV) with cerium(IV) sulphate, using ferroin is redox indicator. The method has been extended to the determination of iron(II) and vanadium(IV) in mixtures.     

Latest achievements in the analytical chemistry of actinides

New methods for separation and determination of actinides, widely used in analysis of actinides in technological and environmental samples are reviewed. Special attention is paid to obtaining and stabilizing transplutonium elements. (TPE) in extreme oxidation states. Their use in analytical practice resulted in expanding possibilities of methods for separation and determination of TPE. Solvent extraction, sorption and extraction chromatography are the basic methods for separation of TPE. Solvent extraction, sorption and extraction chromatography are the basic methods for separation of TPE. Methods of separation in gas phase and some other methods such as precipitation and coprecipitation are applied, however, to a lesser degree. Trends of development of these methods including those of various types of membrane extraction that succeeded in separation of TPE in both trivalent and other valence states have been shown. Attention is paid mainly to consideration of modern methods for determination of actinides, special distinction of such methods being low limits of determination, high precision and selectivity. Alpha- and beta-spectrometric methods with semiconductor detectors are the most advanced among various methods based on registration of nuclear radiation. Tremendous success has been achieved in development of emission-spectrometric methods for determination of trace amounts of actinides and various impure elements occurring in samples of actinides. Sensitive mass-spectrometric methods are widely used for determination of both isotope composition and content of elements in various samples including those which are highly radioactive. More simple and precise titrimetric methods based on using oxidizing-reducing or complexing agents are developed successfully. A large number of coulometric methods for determination of americium and berkelium, characterizing high precision and selectivity as well as luminescence methods have been developed.     

Sequential injection technique for automated titration: spectrophotometric assay of vitamin C in pharmaceutical products using cerium(IV) in sulfuric acid

For the first time sequential injection analysis (SIA) technique has been employed for titrimetry. A new SI titrimetric spectrophotometric method for the assay of vitamin C in drug formulations was explored. The method is based on the oxidation reaction of vitamin C with cerium(IV) in sulfuric acid media using a spectrophotometer as a detector with the wavelength monitored at 410 nm. A 2(3) factorial design chemometric approach was employed to study the interaction effect of the chemical and system variables, mainly cerium(IV), sulfuric acid concentrations and the flow rate. The results of the chemometric optimization revealed that the optimum operating conditions for the SI titrimetric analysis of vitamin C were 7.0 x 10(-3) M cerium(IV), 0.455 M sulfuric acid and 28.9 microL s-1 flow rate. A linear calibration plot for the determination of vitamin C was obtained in the concentration range between 30 to 200 ppm. The method was applied to the determination of vitamin C in pharmaceutical preparations and no excipient was found to pose any interference, thus rendering the method suitable for the determination of the drug in pharmaceutical preparations. The SIA method is found to be accurate when the results were statistically compared with the results obtained by the BP standard method. The SIA method is superior when compared to the conventional titration method, the BP standard method and previous methods with respect to precision and automation in solution handling.     

Monte Carlo simulations for predicting the precision of results and for optimizing data acquisition schedules

Monte Carlo simulations can be used to determine the precision of an analytical method if the standard deviations of the component unit operations are estimated accurately. Alternative methods for estimating the standard deviation have been compared by evaluating the success of Monte Carlo simulations to predict the precision of a second-order rate constant determined by spectrophotometry and of an equivalent weight and acid dissociation constant determined by potentiometry. Monte Carlo simulation has also been used with simplex optimization to predict a data acquisition schedule which gives high precision in the equivalent weight determination. By comparison with a naive design, a 22-fold improvement was predicted. A 15-fold improvement was observed experimentally.     

Titrimetric determination of uric acid with manganese(IV) sulfate

A simple indirect titrimetric determination of uric acid with manganese(IV) sulfate has been proposed. The method is stoichiometric and accurate and can be conveniently adapted for the assay of urinary uric acid.     

Titrimetric micro determination of some phenothiazine neuroleptics with potassium hexacyanoferrate(III)

Three simple, rapid and accurate titrimetric procedures using potassium hexacyanoferrate(III) have been developed for the micro determination of five phenothiazine drugs in pure form and in dosage forms. The procedures are based on the oxidation of phenothiazines in an acid medium to colourless sulphoxides via orange or purple coloured products. In the first procedure, phenothiazines are titrated directly in H(2)SO(4)-H(3)PO(4) medium to a colourless end point. In the second method, a known excess of the oxidant is added and after a specified time, the residual oxidant is determined iodometrically. The third method employs electrometric end-point detection. The optimum reactions conditions and other analytical parameters are evaluated. The influence of the substrates commonly employed as excipients with phenothiazine drugs has been studied. Statistical comparison of the results with those of an official method shows excellent agreement and indicates no significant difference in precision.     

Benzidine and its derivatives in analytical chemistry

A survey has been made of the analytical applications of benzidine and diphenylamine and their derivatives, as precipitants, in the detection and colorimetric determination of oxidants and as indicators in titrimetric analysis. The period covered is from the beginning of 1946 to the end of 1958.