Colorimetric determination of nitrites with p-diaminodiphenylsulphone-diphen-ylamine as reagent

Diaminodiphenylsulphone-diphenylamine is used in a new colorimetric method for the determination of nitrite over a range of 0.1-2.5 mg/l . at pH 1.8 and 0.22-0.4 mg/l . at pH about 0.1. The coloured solutions are stable, follow Beer's law and are suitable for determination of traces by visual comparison. The method is selective and neither chlorine nor nitrogen trichloride gives similar colour reactions.     

The determination of organochlorine pesticides and polychlorinated biphenyls by combustion tube decomposition and molecular emission cavity analysis

The determination of microgram quantities of chlorine in polychlorinated biphenyls and organochlorine insecticides by molecular emission cavity analysis is described. Samples either pure, in admixture or mixed with sand were decomposed at 900 ± 50°C in a quartz combustion tube in a humidified oxygen atmosphere. The products of decomposition were bubbled through water or 1% ammonia and 4-μl aliquots of the solution obtained were injected into a stainless steel indium-lined cavity and heated in a nitrogen/hydrogen flame. The chlorine was quantified by comparing the intensity of the InCl emission at 360 nm with that obtained from hydrochloric acid standards. The effect of potential interferences such as alkali and alkaline earth metals, nitrogen, phosphorus, sulphur, carbon aluminium and iron were studied. Except for the alkali and alkaline earth elements, the recoveries of the compounds burned were not affected. Where the elements interfered, methods for eliminating the interferences are described. The chlorine recovery was usually >90%.     

Inhibitive Effect of Butyltin Trichloride on Dissolution and Localized Corrosion of Aluminium in Sodium Hydroxide and Hydrochloric Acid

The dissolution of aluminium in sodium hydroxide and hydrochloric acid in the presence of butyltin trichloride as corrosion inhibitor has been studied by hydrogen evolution and thermometric methods. Experimental findings indicate that the inhibition effect of butyltin trichloride takes place through an adsorption mechanism following the Frumkin's isotherm. Butyltin trichloride acts as a weakly adsorbed inhibitor in NaOH and as a strongly adsorbed inhibitor in hydrochloric acid medium.     

Chemiluminescence flow system for the determination of ammonium ion

A novel chemiluminescence (CL) system for ammonium ion combined with flow-injection analysis is presented in this paper. It is based on the CL reaction between luminol, immobilized electrostatically on an anion-exchange column, and chlorine electrochemically generated on-line via a platinum electrode from hydrochloric acid in a coulometric cell. Ammonium ion reacts with chlorine and decreases the observed CL intensity. The system responds linearly to ammonium ion concentration in the range 1.0-100 muM, and the detection limit is 0.4 muM. A complete analysis, including sampling and washing, could be performed in 1 min with a relative standard deviation of <6.0%. The system is stable for over 500 determinations and has been applied successfully to the determination of ammonium ion in rainwater samples.     

Determination of tin in titanium alloys

Tin-titanium alloys are becoming increasingly important; consequently a good method is needed for the determination of tin in this type of material. In this paper an accurate iodometric procedure is proposed for the determination. The sample is dissolved in sulfuric acid and the titanium oxidized with potassium permanganate. Tartaric acid is added and the tin precipitated with hydrogen, sulfide. The sulfide precipitate is dissolved in a mixture of sulfuric, perchloric and nitric acids and the solution evaporated to fumes of sulfuric acid. Water and hydrochloric acid are added, and the tin is reduced with lead and antimony trichloride and titrated with iodine. A study was made of the interfering elements that might be found in titanium alloys. The effect of antimony trichloride in reducing interference from copper was investigated. The method is recommended for titanium alloys containing 0.05 to 5.0 per cent. tin.     

酸性氯酸钾处理-水浴加热全自动凯氏定氮仪测定土壤矿物中的固定态铵

固定态铵作为一种重要的潜在氮源,准确测定其含量,对于认识土壤肥力的形成机理、生态系统氮循环和保障国家粮食安全具有十分重要的意义。固定态铵最常用的方法是Silva-Bremner法,但该方法试剂配制要求严苛,前处理过程操作繁琐、费时。为了实现快速、准确、安全地测定土壤固定态铵的含量,对前处理过程进行了研究,用酸性氯酸钾溶液处理土壤样品,用水浴代替震荡,并与Silva-Bremner法的结果进行了对比。试验了自动凯氏定氮仪工作参数、酸性氯酸钾的浓度和用量、水浴加热的温度和时间,确定了测定土壤固定态铵的最佳条件。结果表明,称取1克样品加入20毫升氯酸钾-盐酸混合溶液（3％-10％）预处理,用0.5mol/L氯化钾溶液交换、洗涤,残渣加入加5mL氢氟酸-盐酸溶液（5mol/L-1mol/L）,在沸水浴加热1.5-2h,用自动凯氏定氮仪蒸馏滴定。对5种类型土壤固定态铵7次测定的结果进行了数据分析,相对标准偏差（RSD）均小于3.87%,最大G值1.49,最大F检验值4.12,最大t检验值0.72,均小于临界值,两种方法测定结果无显著差异。该方法的操作安全性和分析效率得到大幅提高,方法的精密度、准确度满足要求。     

Spectrophotometric determination of the pH scale in ethane-1,2-diol

A highly selective method is described for the determination of gallium at the ppm-level in manganese nodules and geological reference samples. After dissolution of the sample, gallium is adsorbed on Dowex 1 (chloride form) from hydrochloric acid solution containing titanium trichloride, which reduces iron(III) so that it is not adsorbed. After elution with dilute nitric acid and evaporation, gallium is determined by atomic-absorption spectrometry with an air-acetylene flame.     

Absorption of chlorine into water

Solubility and diffusion data have been used to describe absorption of chlorine into water. When the gas dissolves in water, hydrochloric acid produced by partial hydrolysis of molecular chlorine diffuses rapidly into the bulk liquid. Because the surface of the absorbent is depleted in hydrochloric acid, the solubility of chlorine in the interfacial liquid is significantly higher than the equilibrium solubility at the same chlorine partial pressure. During desorption of dissolved chlorine, hydrochloric acid diffuses from the interior and collects in the interfacial region. Differential equations for absorption and desorption with coupled flow of a second solute component are solved numerically. Calculated concentration profiles are in good agreement with profiles estimated by chemical analysis of layers of absorbent.     

Determination of sorbic acid with sodium chlorite

A new method for the determination of sorbic acid is proposed, using sodium chlorite in hydrochloric add medium as reagent. In these conditions the hydrochloric acid is oxidized to chlorine which adds on to the double bonds of the sorbic acid. The addition is rapid (30-90 sec) and for this reason the determination is more rapid then others similar to it. Sorbic acid has been determined in foods by this method, after a preliminary solvent extraction or steam-distillation.     

Spectrophotometric determination of some dibenzazepine drugs by electrophilic coupling

Two sensitive spectrophotometric methods for the determination of imipramine hydrochloride, clomipramine hydrochloride, desipramine hydrochloride, and trimipramine maleate in bulk and in dosage forms are described. The first method is based on the interaction of diazotized p-nitroaniline (DPNA) with the dibenzazepine drug in 5M hydrochloric acid. The second is based on the oxidative coupling of the dibenzazepine drug with 3-methylbenzothiazolin-2-one hydrazone (MBTH) in the presence of ammonium iron(III) sulphate in 0.1M hydrochloric acid. The resulting chromophores are measured at 575 nm (for the DPNA method) or at 620-630 nm (for the MBTH method), and are stable for at least 24 hr. The commonly encountered excipients and additives do not interfere with the determinations. Results from the analysis of pure drugs, commercial tablets and laboratory-prepared tablets by these methods agree well with those of official methods.     

The determination of tin in tin ores and concentrates by atomic absorption spectrophotometry in the nitrous oxide-acetylene flame

Tin in tin ores and concentrates can be determined by atomic absorption measurement in the nitrous oxide-acetylene flame. Solutions are prepared by heating the samples with ammonium iodide and dissolving the resulting tin iodide in dilute hydrochloric acid. Calibrating solutions contain ammonium iodide and hydrochloric acid at approximately the concentrations present in the sample solutions. The method has a limit of detection of 0.02% tin in the sample and is suitable for application to geochemical prospecting samples. The results are similar to those obtained by standard chemical methods.     

Atomic-absorption spectrophotometric determination of tin by hydride generation in non-aqueous medium after extraction

Tin at the microgram level was extracted into chloroform with N-nitrosophenylhydroxamic acid (ammonium salt) from 0.5-1.5M hydrochloric acid medium. Tin hydride was generated from 1 ml of the chloroform extract mixed with 3 ml of 1% sulphuric acid solution in N,N-dimethylformamide. by injection of 3 ml of 2% sodium tetrahydroborate solution in N,N-dimethylformamide through the septum of the hydride generator. Tin was then determined by AAS at 224.6 nm with an acetylene-air flame, and nitrogen as carrier gas. The peak-height of the signal was linearly related to amount of tin up to 20 mug. The sensitivity of the determination was improved by the extraction. The method was applied to determination of tin in tinned foods and aluminium-base alloys with good accuracy and precision.     

Synthesis of disodium hydroxotetranitronitrosylruthenate

It was found that the reaction of sodium nitrite with ruthenium trichloride proceeds at room temperature even without hydrochloric acid, giving disodium hydroxotetranitronitrosylruthenate /Na₂RuNO/NO₂/₄OH/. No appreciable amount of nitrogen oxide evolved in the reaction.     

Spectrophotometric determination of calcium in zirconium powder by use of murexide

An accurate spectrophotometric method is proposed for the determination of calcium in zirconium powder by use of murexide. A 0.4-g sample is dissolved in hydrofluoric and sulphuric acids, the solution evaporated to fumes of sulphuric acid, and a mercury cathode electrolysis made if more than 0.05% copper or nickel is present. Ammoniacal precipitation in the presence of ammonium chloride separates zirconium and other elements and an aliquot of filtrate is collected, equivalent to 0.2 g of sample. The ammonium salts are destroyed with nitric and hydrochloric acids and the calcium is determined with murexide. The high reagent blank is shown to be due to the reagent grade nitric acid, hydrochloric acid, and ammonium hydroxide.     

Hydride Generation Atomic Fluorescence Spectrometric Determination of Ultratrace Arsenic in High Purity Indium Oxide

A simple, sensitive, and interference free method was proposed for the determination of total arsenic in high purity indium oxide by hydride generation atomic fluorescence spectrometry (HG-AFS). Preconcentration was carried out by distillation of volatile arsenic trichloride. Hydrazine sulfate was used as a prereductant to reduce As (V) to As (III). The volatile arsenic trichloride generation was based on the reaction between As (III) and hydrochloric acid, and vapors were absorbed with water. The method provides a linear response range of 2 ng/mL–70 ng/mL, a detection limit of 0.1 ng/mL, a recovery of 96%–113%, and an average relative standard deviation of 2.42%. The method was validated by means of interlaboratory comparative analysis with the proposed method HG-AFS, and the comparison of data by using proposed method HG-AFS and reference methods of ICP-OES and spectrophotometry.     

A fluorescent nitrate sensing system using a reaction cartridge and titanium trichloride

A simple and highly sensitive cartridge type nitrate sensing system was developed using titanium trichloride (TiCl(3)) in hydrochloric acid to reduce nitrate to ammonium ion. The system primarily consisted of a nitrate reduction section using titanium trichloride and an ammonia detection section. The nitrate was reduced in a simply made cartridge equipped with filter units and the resulting ammonium ion solution was directly introduced into a flow injection system, where it was neutralized to ammonia and allowed to react with o-phthalaldehyde (OPA). The isoindole thus formed was detected by virtue of its fluorescence, allowing quantitation of the nitrate in the initial sample. Our sensing system has a detection limit of 0.01 mg l(-1) and a dynamic linear range from 0.05 to 2.5 mg l(-1) with response times of less than 5 min for the entire procedure. The system had a relative standard deviation (RSD) of less than 2.56% after more than 30 consecutive measurements of 0.5 mg l(-1) NO(3)(-). The system is unaffected by FeCl(3), Na(2)SO(4) and NaCl at concentrations of 200 mg l(-1) or by biological oxygen demand (BOD) values as high as 110 mg O l(-1). The effects of reaction time and titanium trichloride concentration were also investigated. Furthermore, several river water samples were examined.     

Determination of boron and nitrogen in boron nitride

Improved techniques are described for the determination of boron and nitrogen in pure boron nitride. Controlled fusion of boron nitride with sodium carbonate in a muffle furnace is followed by a potentiometric titration of the boric acid. A special quartz vessel is described for the determination of nitrogen. The boron nitride is fused with sodium hydroxide and the resulting ammonia is swept into a receiver and titrated with standard hydrochloric acid. Boron and nitrogen values with their standard deviation are given for a typical pure boron nitride.     

Protonation and solvent extraction of N-p-tolylbenzohydroxamic acid in hydrochloric acid medium

the protonation of N-p-tolylbenzohydroxamic acid (p-TBHA) in aqueous hydrochloric acid has been investigated by determination of its distribution between cyclohexane and hydrochloric acid. The pK(a) value found was - 2.30 +/- 0.02 at 30 degrees . The solubility of p-TBHA as a function of hydrochloric acid concentration has also been determined. At lower acid concentrations the solubility decreases owing to a salting-out effect, whereas at higher concentrations it increases because of formation of the more hydrophilic protonated species and a salting-in effect. Intramolecular hydrogen-bonding observed in p-TBHA provides evidence for protonation of the nitrogen atom.     

Use of complexing ligands in the determination of antimony and tin by atomic-absorption spectrometry

The atomic-absorption spectrophotometric determination of antimony is best achieved in the presence of either an ammonium fluoride, hydrochloric acid, nitric acid mixture, or one of the following complexing agents: tartaric acid, citric acid, oxalic acid, 2-mercaptopropanoic acid. The interference of the 29 metals tested is least in the ammonium fluoride-hydrochloric acid-nitric acid mixture and is similar in tartaric acid, citric acid and 2-mercaptopropanoic acid media. However, the interference is pronounced in oxalic acid. Tin can be determined if any of the complexing agents or 6M hydrochloric acid is present.     

Microcoulometric Determination of Sulfur and Chlorine by Combustion and Nitrogen by Hydrogenolysis

Abstract

The design of an improved open microcombustion tube and experimental conditions for the rapid, accurate and precise determination of sulfur and chlorine by microcoulometry are described. The design and operating conditions for a catalytic hydrogenolysis tube and scrubber tube for acid removal are also presented for the determination of nitrogen. Examples of the application of the above methods for these elements in petroleum and petrochemicals are presented.