p-nitroaniline as a colorimetric reagent for sulphur dioxide

The merits of the nitroanilines as an alternative to p-rosaniline and fuchsine in the colorimetric determination of sulphur dioxide and sulphites have been investigated. p-Nitroaniline was found to be a stable, well-defined reagent, with which sulphur dioxide can be determined to a high level of precision, the sensitivity being of the same order of magnitude as for p-rosaniline.     

The use of silver vanadates as absorbents for sulphur dioxide

A new solid absorbent for sulphur dioxide is described which is effective at room temperarures, and which does not absorb carbon dioxide. Exhaustion of the filling is indicated by a change in colour from green to brown.The reagent is prepared by heating molecular quantities of silver oxide and silver metavanadate together at 150° C. Evidence is given that on such treatment the two silver salts combine, forming a product having the same empirical composition as silver orthovanadate but different as regards its properties from the orthovanadate produced by the usual precipi-tation method.     

4,4-Acetalidine-bis-(3-methyl isoxazolone-5) as a new colorimetric reagent for the determination of palladium and uranium

Summary Palladium and uranium react with 4,4-acetalidine-bis-(3-methyl isoxazolone-5) in acid medium to give yellow color having a visual limit of identification at 2 and 15g per ml. This color reaction provides the basis of a new method for colorimetric determination of palladium and uranium. Copper also gives yellow color but it cannot be determined with this color reaction because the color intensity is not stable. The maximum tolerable limit of various ions is reported.

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Zusammenfassung Pd und U reagieren in saurem Milieu mit 4,4-Acetalidin-bis-(3-methyl-isoxazolon-5) unter Gelbfärbung mit einer Erfassungsgrenze von 2 bzw. 15g/ml. Diese Farbreaktion dient als Grundlage für eine neue kolorimetrische Methode für Pd und U. Cu gibt zwar auch eine Gelbfärbung, kann aber damit nicht bestimmt werden, da die Farbintensität nicht beständig ist. Die maximal tolerierbare Menge der Fremdionen wird angegeben.

     

Synthesis of poly(sulfonium cation) as an alkylating reagent

Methyl 4-phenylthiophenyl sulfoxide is polymerized to poly(methyl-4-phenylthiophenylsulfonium) in poly(phosphoric acid) with a yield higher than 90%. The demethylation of poly(sufonium cation) is examined to control the composition ratio of the thiophenylene unit in the polycation. The polycation is soluble in common solvents due to the alternative structure of phenylene sufide and phenylenesulfonium cation and is easily converted to poly(phenylene sulfide) through the demethylation with a nucleophile. The poly(sulfonium cation) can be applicable as an alkylating agent for phenol, aniline and benzoic acid to the corresponding to anisole, N-methyl aniline, N,N-dimethyl aniline and benzoic methyl ester, respectively, with high conversion through the demethylation. These products can be isolated without a complicated purification because poly(phenylene sulfide) is precipitated in the mixture as the side product due to the poor solvent solubility.     

A new indirect spectrophotometric procedure for determination of sulphur dioxide

An operationally inexpensive and sensitive spectrophotometric procedure for sulphur dioxide is proposed. The reagent 5,5-dimethyl-1,2,3-cyclohexanetrione-1,2-dioxime-3-thiosemicarbaz one is used to determine trace amounts of sulphur dioxide indirectly by means of the reduction of Fe(III) to Fe(II). The method can determine down to 0.032 microg/ml of sulphur dioxide in the final solution and recoveries are better than 98%. The method can be applied to the determination of atmospheric SO(2) provided that interfering gases such as nitrogen dioxide and hydrogen sulphide are eliminated.     

Palladium (II) chloride as a reagent for the mild aromatization of piperidine and cyclohexanone

Summary Piperidine may be rapidly converted into pyridine using palladium(II) Chloride or tetrachloropalladate(II) ion in aqueous medium at pH 10-11 and in the absence of oxygen. Cyclohexanone may be aromatized under the same conditions, although more slowly. The products fromo-cyclohexenylcyclohexanone are also described.     

Barium oxalate as a selective solid reagent for the absorption of sulphur trioxide

Barium and calcium oxalate monohydrates have been shown to be more suitable absorbents for sulphur trioxide than either anhydrous or hydrated oxalic acid. All four compounds are selective absorbents for the trioxide and do not absorb sulphur dioxide. Similarly all are elective absorbents for sulphuric acid aerosol, although the calcium salt may be decarboxylated under these conditions. Lead oxalate and formate may be suitable for the absorption of SO(3) and H(2)S, and SO(3), H(2)S and SO(2) respectively.     

Automatic enzymatic determination of glucose with a potentiometric sulphur dioxide probe

An automatic, continuous-flow system for the determination of glucose is reported, with a sulphur dioxide probe used as the sensor for an indicator reaction with hydrogensulphite. In the presence of glucose oxidase, glucose is selectively oxidised to produce hydrogen peroxide at a rate proportional to the glucose concentration. The oxidation of hydrogensulphite by the hydrogen peroxide is rapidly monitored by the probe at sampling rates as high as 90 samples per hour. Proteins and reducing substances, such as cysteine, uric acid and ascorbic acid interfere only in large amounts. The method is applicable to biological fluids without prior separation steps.     

Hydrazinium thiocyanate as a reagent for determination of copper

Hydrazinium thiocyanate, N(2)H(5)SCN, has been used for the determination of copper in copper salts. The reagent reduces the copper ions to the cuprous state and precipitates cuprous thiocyanate Cu(2)(SCN)(2), quantitatively.     

Resorcinol as an analytical reagent for the spectrophotometric determination of uranium

A spectrophotometric study of the reaction of uranyl acetate and resorcinol shows that an orange-red coloured resorcinolate of composition 1:2 is formed. This colour reaction can be conveniently used for the spectrophotometric estimation of uranium at PH 4.72.     

The determination of thiols with diphenylpicrylhydrazyl as a spectrophotometric reagent

Diphenylpicrylhydrazyl (DPPH), a stable, intensely purple free radical, is used as a reagent in the quantitative determination of various aromatic and aliphatic thiols by indirect spectrophotometric analysis. Plots of degree of reaction vs. time show that thiophenol and its derivatives react more quickly than aliphatic thiols with DPPH. Calibration plots are linear over the concentration range 0.05-3.00 x 10(-5)M thiol. The average relative error is in the range 1-2% and the absolute standard deviations range up to 0.50 x 10(-6)M.     

Synthesis,structural characterization and biological activity of polyoxometallate-containing protonated amantadine as a cation

A novel isopolyoxomolybdate complex (C₁₀H₁₈N)₄Mo₈O₂₆·6(CH₃)₂SO 1 was synthesized, purified and characterized by means of elemental analysis, IR and ¹H NMR spectra and single-crystal X-ray diffraction. It crystallizes in a triclinic system with a?=?11.5090(6), b?=?12.8399(3), c?=?14.774(13)?Å, α?=?105.390(16), β?=?93.09(4), γ?=?106.100(10)°, V?=?2003.1(2)?ų, Z?=?2, R1?=?0.0789, wR2?=?0.2190. Complex 1 is constructed from [Mo₈O₂₆]^4?, (C₁₀H₁₈N)⁺ and (CH₃)₂SO and extends to form a two-dimensional network via hydrogen bonds and weak interactions in the ab plane. Chicken embryo experiments show that Compound 1 has high antiviral activity in vitro.     

Metavanadate as a reagent for the colorimetric determination of acids

Acids with pK(a) > 6 can be determined colorimetrically by their reaction with metavanadate, provided they are not coloured and do not give complexation or redox reactions with the polyvanadate.     

Arsenazo III as a spectrophotometric reagent for determination of lead

Arsenazo III is proposed as a spectrophotometric reagent for the determination of lead. The complex formation begins at pH > 2 and is greatest at pH 4-6. The molar absorptivity of the complex has a mean value of 2.8 x 10(4) 1.mole(-1).cm(-1) at 600 nm and remains nearly constant in the pH range 4-8. The ionic species taking part in the reaction are studied and the equilibrium constants for the different possible reactions are calculated. According to the values obtained, the reaction of PbOH(+) with H(5)L(3-) is predominant. The reaction studied is applied for the determination of micro amounts of lead in technical aluminium.     

Trichlorophenoxyacetic acid as a reagent for the determination of Thorium

2:4:5-trichlorophenoxyacetic acid has been successfully used for the determination of thorium. It has been proved to a better reagent for thorium than 2:4-dichlorophenoxyacetic acid as it produces quantitative precipitation of thorium at a considerably lower pH value and can separate Th from a number of common elements, such as Ca, Ba, Sr, Zn, Co, Ni, Ti, U, etc. and cerite earths more effectively. Zr and Fe interfere, but iron may be removed by a convenient method. Direct weighing may be applicable for the estimation of thorium within the limites of experimental error,     

Iodine trichloride as an analytical reagent for determination of some organic compounds

Procedures are described for the determination of organic compounds with iodine trichloride under Andrews's titration conditions. Samples are directly titrated with iodine trichloride or first reacted with an excess of iodine monochloride, with subsequent titration of the iodine formed. The direct titration is done initially in feebly acid medium, then the acidity is raised (biotin, methionine, cystine and thiomersal). Pre-oxidation with iodine monochloride is used if the organic compound reacts slowly [tryptophan and arsenic(III) compounds] or is determined in bicarbonate medium (hydroxylamine and thiosemicarbazide). The ferrocyanide formed by the reduction of ferricyanide (by thiourea and allylthiourea) can also be titrated. Arsenic(V) compounds are determined after reduction to arsenic(III), and iodine in organic compounds is converted into iodide by alkaline fusion into iodide and the iodide titrated.     

Determination of sulphur and total sulphur dioxide in wines by an ICP-AES method

Sulphur contents of the original sample and the sample free from sulphur dioxide were determined by ICP-AES following nitric acid digestion under high pressure (using PAAR HPA equipment), and the total sulphur content was calculated from the difference between the results obtained. With the aim of preparing a sample free from sulphur dioxide, bound sulphur dioxide was released by sodium hydroxide, then after acidifying by phosphoric acid, boiling was carried out. Relative standard deviations of the results obtained for total sulphur, the sulphur without S(IV) and total sulphur dioxide were lower than 2.5, 3.5 and 5% respectively. Various amounts of sulphur (in the form of Na₂SO₄), added to wine samples, were successfully recovered between 95.5 and 104.9%. Based on comparative analyses performed by a widely accepted classic method, the indirect method developed was found to be adequate for the determination of total sulphur dioxide. The procedure is suitable for serial tests.