A titrimetric method for the rapid determination of carbon in steel with an aqueous titrant

It is demonstrated that the addition of 5% of water to the non-aqueous solvent for the titrimetric determination of carbon in steel improves the performance of the titration. Modifications to the procedure are proposed which allow the normal titrant, tetra-n-butylammonium hydroxide dissolved in benzene-methanol, to be replaced by an aqueous solution of potassium hydroxide. The proposed procedure has been applied to the analysis of a wide range of standard steel samples.     

Analytische und radiometrische Bestimmung kleiner Mengen14CO2

After absorption in an aqueous solution of 0.1 N barium hydroxide the carbon dioxide is determined with an accuracy of ± 0.3% by back titration of the excessive base. From the¹⁴C containing barium carbonate formed the carbon dioxide is liberated again with cone, sulphuric acid in vacuo, and its specific activity is determined. The measurement of activity is performed with a vibrating reed electrometer in an ionization chamber. The mean error of the average value of the activity determination is ± 0.5%.     

Coulometric titration of carbon dioxide on the micro scale

A method is described for the coulometric titration of milligram and submilligram amounts of carbon dioxide. Carbon dioxide is absorbed and titrated in dry acetone containing about 0.5% of methanol and saturated with potassium iodide, in a two-compartment cell. Thymol Blue is used as visual indicator. Current integration is carried out by means of a low inertia motor or a solid-state integrator. The generation efficiency is 99-100%. The method has been applied to the determination of small amounts of carbon (0-1 mg) in organic and inorganic materials and in aqueous solution.     

沉淀双点滴定法测定盐酸左旋咪唑

以Ag^＋作滴定剂,分别用双点滴定法和传统电位滴定法对盐酸左旋咪唑片进行了测定。试液的配制采用了过滤和不过滤两种方法。测定结果表明：所有方法测得的结果均在《药典》允许的范围之内;本法测定结果与《药典》规定方法的对照偏差约为2%-3%;采用过滤和不过滤两种方法配制试液的测定结果之间的偏差约为1%。     

Use of vitreous carbon as a working electrode in coulometric titration of potassium hydrogen phthalate

The use of a vitreous carbon electrode as a cathode in the amperostatic coulometric titration of aqueous potassium hydrogen phthalate solution is described. It is shown that 10 mg of the phthalate can be titrated with a precision better than 0.5%. Current-voltage curves for platinum and vitreous carbon cathodes show that there is an overpotential on the latter relative to the former.     

Direct titration of carbon dioxide

A brief survey is given of the most important methods for the determination of carbon dioxide, and the suitability of these methods is briefly discussed.Details are given of a direct carbon dioxide titration method developed for the detection and determination of substances separated on a gas-liquid partition column.The titration is performed in pyridine or acetone as a solvent and with a sodium methylate solution as a titrant.Results are given of determinations of carbon dioxide in air and, on semi-micro and micro scales, of carbon dioxide obtained by combustion of organic compounds.It is suggested that the proposed method will be generally applicable, e.g.: (1) to the micro and semi-micro determination of carbon and oxygen, (2) to the determination of carbon dioxide formed in wet-combustion analysis, (3) to the determination of carbon in steel.     

Properties of silicas chemically modified by monodentate amines studied by conductometry

The protonation of aminoalkyl groups covalently bonded on the silica surface was studied by the conductometric titration method. Porous varieties of silica can adsorb HCl from an aqueous solution. Conductometric titration was proposed for the determination of concentrations and constants of protolytic equilibrium of grafted amino groups. During HCl chemisorption the effect of temperature on the electric conductivity of suspensions of the modified silicas was studied. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1789–1793, August, 2005.     

Quantitative determination of olefin oxide, chlorohydrin, and cyclocarbonate in the presence of each other

A procedure was developed for the quantitative determination of olefin oxide, chlorohydrin, and cyclocarbonate simultaneously present in the reaction mixture of the synthesis of cyclocarbonate from olefin oxide and CO₂. To determine olefin oxide, an acetone solution of hydrochloric acid was added to a portion of the reaction mixture, and the excess of hydrochloric acid was titrated with an aqueous solution of potassium hydroxide with visual detection. The concentrations of chlorohydrin and cyclocarbonate were calculated from the data of the potentiometric titration of the same solution to which excess potassium hydroxide was added. Deceased.     

Concentration and Thermodynamic Stability Constants of Magnesium(II) and Calcium(II) Tartrate Complexes in Aqueous Solutions

The formation of calcium and magnesium tartrate complexes was studied by potentiometric titration at ionic strengths of 0.1 and 0.3 (in the presence of tetraethylammonium chloride) at a temperature of 298.15 K. The composition and the stability constants of the complexes formed in the system were determined. The known stability constants were used to optimize the conditions of calorimetric determination of the heats of formation of calcium and magnesium tartrates in an aqueous solution.     

Determination of sulfate and sulfur in inorganic and organic materials

Sulfate is determined by titration with lead nitrate solution in aqueous acetone solutions buffered with nitric acid-pyridine, in presence of dithizone indicator. Sulfate is titrated directly or after separation from interfering ions and other materials on a column containing aluminum oxide and cation-exchange resin. The titration and separation are also applied to determination of sulfur in organic compounds after oxygen flask combustion. Details of the methods are fully discussed.     

Potentiometric study of end-point detection in the coulometric determination of carbon dioxide

The coulometric determination of carbon dioxide is based on the alkalimetric titration of the product of absorption of carbon dioxide in an organic solution of monoethanolamine. The processes occurring in various solvents have been investigated and optimized for analytical application. The protolytic reactions of 2-hydroxyethylcarbamic acid have been investigated in 2-propanol + 2, 5 and 10% water, dimethylformamide + 2% water, dimethylsulphoxide +5, 10 and 20% water. In coulometric generation of the base, 0.1M solutions of tetraethylammonium bromide in these solvents were used. The course of the titration was followed potentiometrically with glass and antimony indicator electrodes. From the titration curves the autoprotolysis constants of the mixed solvents and protonation constants of monoethanolamine in them were calculated. These constants and the concentration of monoethanolamine influence the size of the end-point break for the titrations. On this basis, optimal conditions for analysis have been selected and the total carbon content in samples of natural waters has been determined.     

Determination of methylmercuric ions by photometric titration with dithizone

A rapid photometric titration titration technique, which makes it possible to determine methylmercuric ions with a sensitivity of 15mug, is described. The titration takes place in 80% aqueous ethanol, which is capable of dissolving the titrant, a chloroform solution of dithizone. It has thus been possible to avoid the difficulties arising from co-extraction phenomena that occur when the extractive titration procedures developed for mercury(II) are applied to the determination of methylmercuric ions. A formate buffer is used to keep the pH in the range 2.5-3.0. The attainable precision is considerably better than 1 %.     

Potentiometric titration of peptides and the starting materials and intermediates of their synthesis. I. Acidimetric determination of N-acetylamino acids

The potentiometric titration of N-acetylamino acids and their sodium salts in nitromethane-acetic anhydride (2:1) with a nitromethane solution of perchloric acid has been investigated. A procedure has been developed for the quantitative determination of N-acetylamino acids in the presence of acetic acid in aqueous solutions. A differentiation determination of N-acetylamino acids and their salts in the presence of sodium acetate has been carried out.     

Thiomercurimetric determination of carbon disulphide, carbonyl sulphide, thiols and hydrogen sulphide by use of 1,3-diaminopropane and tributyltin chloride

A new approach to the determination of carbon disulphide and carbonyl sulphide in the presence of each other is based on the reaction with 1,3-diaminopropane (DAP), and titration with o-hydroxymercurybenzoie acid (HMB) before and after the selective decomposition of the COS-derivative at pH 4. Determination of hydrogen sulphide, thiols, carbon disulphide and carbonyl sulphide in the presence of each other in hydrocarbon solvents involves four titrations with HMB, viz. of all compounds after conversion of CS(2) and COS with DAP, of thiols plus H(2)S, of the thiols alone after removal of H(2)S by extraction, and of CS(2) alone after removal of other compounds by shaking with aqueous alkali. For selective trapping of H(2)S, HCN, RSH, CO(2) and CS(2) + COS, the sample gas is passed successively through a potassium antimonyl tartrate filter, a nickel carbonate filter, a tributyltin chloride filter, a bubbler containing 40% potassium hydroxide solution and a bubbler containing a benzene solution of DAP. The analysis is completed by titration with HMB with dithizone or dithiofluorescein as indicator.     

The coulometric determination of salicylate in serum

Constant-current coulometry can be used for the determination of salicylate in 100 μg of blood serum. The titration is preceded by extraction of acidified serum with ethylene dichloride followed by removal of the salicylate to an aqueous solution of pH 7.5 tris(hydroxymethyl)aminomethane buffer which also contains copper(II) sulfate to enhance recovery. A residual titration with bromine as titrant followed by addition of potassium thiocyanate is used because of the slow bromination of salicylate. Serum samples containing salicylate in the range 4–60 mg/100 ml were analyzed. Recoveries of about 90% were obtained.     

Amperometric Determination of Cholesterol-Reducing Drug,Ezetimibe, Using Glassy Carbon Electrode Modified with Multiwalled Carbon Nanotubes and Sodium Dodecylsulfate

A simple and sensitive electrochemical method is described for the determination of the cholesterol-reducing drug ezetimibe in aqueous solution. A glassy carbon electrode, modified with multiwalled carbon nanotubes and sodium dodecylsulphate was used as the working electrode. Ezetimibe yields a well-defined anodic peak at the surface of the electrode in an aqueous solution of pH 13. A linear amperometric calibration curve was obtained in the range of 1.2–78 μM (0.5–32.0 μg/mL) of ezetimibe, with a sensitivity of 88.6 nA/μM and a detection limit of 300 nM (0.12 μg/mL). The sensor was applied successfully to the determination of ezetimibe in pharmaceutical preparations.     

Determination of ibuprofen and novocaine hydrochloride with the use of water-micellar solutions of surfactants

The solubility and acid-base properties of ibuprofen in water-micellar media of surfactants were studied. A new visual method for the titrimetric determination of ibuprofen in pure form was proposed. The smallest pK value (4.43) and the greatest solubility (8.1 mg ml⁻¹) of ibuprofen were achieved using an aqueous cationic micellar medium of 0.1 M tridecylpyridinium bromide. The titration was performed with 0.05 M potassium hydroxide aqueous solution and the exact end-point was determined with the use of xylenol blue as indicator. Conditions for the individual determination of ibuprofen and novocaine hydrochloride in their 1:1 mixtures with the use of 0.1 M tridecylpyridinium bromide were proposed.     

Determination of metallic iron in a mixture of lime, calcium sulphide and pyrrhotite

A method is described for the determination of metallic iron in a complex matrix consisting of calcium oxide, calcium sulphide, carbon and pyrrhotite. The procedure consists of leaching the sample with 5% ammonium chloride solution (10% sucrose solution in some cases) followed by treatment with mercury(II) chloride solution and titration with dichromate solution.     

Die analytische anwendung der kohlendioxyddestillationUntersuchung von dekarboxylierungsreaktionen in wässriger lösung

Carboxylic acids which decompose spontaneously on boiling or by oxidation in aqueous solutions can be determined by titration of the carbon dioxide formed after distillation as described previously. Acetonedicarboxylic acid and p-aminosalicylic acid are determined by spontaneous decarboxylation. Hydrolysis must precede the determination for acetoacetic ester, phenylethylcyanoacetic ethyl ester and for carbonic acid esters. Oxidative decarboxylation allows determinations of glyoxylic acid, aldonic acids, sugar dicarboxylic acids, formic acid, oxalic acid and α-amino acids. The titration of the carbon dioxide formed can be done with 0.1 or 0.01 N solutions. The interference of atmospheric carbon dioxide is avoided by the use of pentane as a sealing liquid.     

Analysis of bismuth base alloys : Ternary alloys containing uranium and neodymium or praseodymium

Procedures are described for the analysis of bismuth base alloys containing 0.2–5% of uranium and 0.2–5% of neodymium or praseodymium. Bismuth is first separated from a solution of the alloy in N nitric acid by extraction with diethylammonium diethyldithiocarbamate in chloroform, followed by the separation of uranium with the same reagent from an acetate buffered solution of pH 5.5–6.0. The uranium determination is completed by measuring the absorbancy of its diethyldithiocarbamate complex in chloroform. The neodymium or praseodymium is determined by titration with EDTA of the aqueous solution remaining after the separation of bismuth and uranium, using xylenol orange indicator in solutions of pH 5.6–5.8 EDTA is also used to determine the bismuth by direct titration of a separate aliquot of the sample solutions.