Simultaneous microdetermination of carbon, hydrogen, chlorine, bromine, sulfur, and metals in organometallic compounds

A method for the simultaneous microdetermination of carbon, hydrogen, chlorine, bromine, sulfur, and metals which combines features of the known intermediate storage technique in organic microanalysis and formation of the metal-oxine complex, is described. Carbon and hydrogen are determined gravimetrically as usual. Sulfur and halogens are absorbed and stored on electrolytic silver. After completion of the combustion, the oxygen is replaced first by nitrogen and secondly by hydrogen which liberates the sulfur as sulfur dioxide and halogens as hydrogen halides and regenerates the silver layer. The liberated gases can be easily absorbed by dilute hydrogen peroxide and determined titrimetrically. The metal oxide, remaining in the platinum boat, is dissolved in a mixture of nitric-perchloric acids in a test tube and the metal content is determined gravimetrically and titrimetrically using 8-hydroxyquinoline.     

A novel combustion system for the microdetermination of nitrogen

A method for the determination of nitrogen by combustion in a fast flow of pure oxygen is described. The oxygen is produced electrolytically and the hydrogen produced simultaneously is used to reduce the excess oxygen and oxides of nitrogen. A short layer of copper oxide oxidizes the hydrogen which remains uncombined due to the oxygen consumption of the sample. This layer is swept out by the water vapor; thus, only minute amounts of carbon dioxide are used, reducing the consumption of potassium hydroxide. The small layer of copper oxide can easily be reoxidized with air or technical oxygen. A virtually unlimited excess of oxygen during the combustion makes this method especially useful for samples difficult to combust and for trace determinations.     

In Process Citation

A rapid simple method is described for the determination of carbon in organic compounds. The technique is based on a flash-combustion of the weighed sample (1-3 mg) in a hot empty combustion chamber at 950-1050 degrees and swept by a stream of oxygen at a rate of 80-100 ml min . Together with this flash and dynamic combustion in oxygen, a cupric oxide filling at 850 degrees is necessary. Halogens and sulphur oxidation products are retained by means of a silvered alumina filling at 750-800 degrees . Water and acidic oxides of nitrogen are absorbed at room temperature by means of magnesium perchlorate and manganese dioxide respectively. Carbon dioxide is absorbed in the cathodic compartment of an automatic coulometer and generates H(+) ions which are neutralized by OH(-) obtained by electrolysis. This method makes possible the determination of carbon in compounds containing halogens (including fluorine), phosphorus and metals. However, some metal compounds with polynuclear rings in their molecules give low results and require the addition of an oxidant to the sample in the boat for complete combustion. Vanadium pentoxide seems to be the best oxidant in the present working conditions. Solid samples are weighed and analysed in platinum or porcelain boats; liquid samples are weighed in Pyrex capillaries which are laid in platinum boats and covered with a small piece of platinum gauze. When normal liquid samples are analysed, one tip of the capillary is broken before its introduction into the combustion tube but in the case of volatile liquid samples the sealed capillary is introduced into the combustion chamber, where it explodes. The precision obtained is better than that of the classical methods.     

Simultaneous microdetermination of carbon,hydrogen, mercury,chlorine, bromine and sulphur in organic compounds

A simple, reliable method for the simultaneous microdetermination of carbon, hydrogen, mercury, chlorine (or bromine) and sulphur in organic compounds is described. The intermediate storage technique is used. Sulphur and the halogens are absorbed on electrolytic silver and determined gravimetrically or titrimetrically. Mercury is absorbed on gold wire, and is weighed as the metal or desorbed and determined by a mercury-8-hydroxy-quinoline method.     

In Process Citation

The method for the determination of sulphur in organic compounds (E. Debal and R. Levy, Bull. Soc. Chim. France, 1968, 426; 1971, 3374) by combustion in oxygen at 1310-1320 degrees C and coulometric titration of the sulphur dioxide formed is improved. Silver and 8-hydroxy-quinoline are successfully used to remove halogens (fluorine included) from combustion products. A new glass cell for the acidimetric titration of sulphur dioxide with an automatic coulometer is devised, with a water-jacket for its cathodic and reference compartments. The constant-temperature water-flow makes this determination easy to carry out with no drawbacks, even in varying ambient temperature.     

Manometric submicro determination of carbon and hydrogen in organic materials

A method is described for the determination of carbon and hydrogen in quantities of organic material ranging from 5 to 50 μg. The method involves catalytic combustion of the sample in oxygen and measurement of the pressures of the resulting carbon dioxide and water. Special attention has been paid to the reduction of the effect of water adsorption in the apparatus. The present submicro method can be applied to non-volatile, non-hygroscopic samples and is free from interferences by nitrogen, sulphur and halogens (except fluorine). The standard deviation in the 50-μg sample range is 0.13% for carbon and 0.10% for hydrogen. The average duration per analysis when carried out in series is 20 min.     

A study of the effect of some pollutant gases on cathodes used in membrane-covered amperometric oxygen detectors

The effects of various gaseous pollutants on the electrochemical activity of materials used as cathodes for membrane-covered amperometric oxygen detectors are described. It is shown that gold and platinum cathodes are not unduly affected by concentrations of sulphur dioxide and chlorine many times greater than those likely to be encountered in test solutions, and that a gold cathode is also unaffected by hydrogen sulphide. A platinum cathode is rapidly and significantly poisoned on contact with hydrogen sulphide; an analysis of the fall in the rate of oxygen reduction as a function of time indicates that the poisoning occurs by the blocking of surface sites by sulphide. The effect of hydrogen sulphide on silver, nickel and nickel sulphide electrodes is also reported. Of these materials, only nickel sulphide is an effective electrocatalyst for oxygen reduction in the presence of sulphide.     

Simultaneous microanalytical determination of carbon,hydrogen and sulphur

Summary A microanalytical procedure for simultaneous determination of carbon, hydrogen and sulphur by combustion in a nitrogen atmosphere is described. The substance is oxidized by the thermal degradation products of silver permanganate (Körbl catalyst) which serve as a source of oxygen and as an absorbent for sulphur oxides. The carbon and hydrogen are determined by the classical methods and sulphur is converted into benzidine sulphate. The procedure is accurate, simple and quick.

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Zusammenfassung Ein mikroanalytisches Verfahren zur gleichzeitigen Bestimmung von C, H und S durch Verbrennung in Stickstoffatmosphäre wurde beschrieben. Die Substanz wird mit dem thermischen Zersetzungsprodukt von Silber-permanganat (Körbl-Katalysator) oxydiert, der als Sauerstoffdonator und als Absorbens für Schwefeloxide dient. C und H werden nach der klassischen Arbeitsweise bestimmt und S in Benzidinsulfat umgesetzt. Das Verfahren ist genau, einfach und rasch.

     

Mikrobestimmung von Kohlenstoff und Wasserstoff,sowie von 14C,Tritium und Deuterium im Stickstoffstrom

A microanalytical method for the determination of carbon and hydrogen is described. The procedure involves the combustion of the organic substance in a stream of nitrogen and the oxidation of the decomposition products with oxygen. Halogens and sulphur are absorbed by the combustion catalyst (according to Körbl), whereas nitrogen oxides are reduced on a copper surface. The combustion products, CO₂ and H₂O are determined gravimetrically; in the case of radioactive samples they are appropriately absorbed and counted in a liquid scintillation counter. Strongly quenching singly and doubly labelled samples, which cannot be accurately counted even by modification of the counting device, give equally high radioactive yields (75% for ¹⁴C, 30% for ³H), since counting is not influenced by other gaseous impurities. Deuterium is quantitatively determined by measuring the intensity of the OD-signal at 2500 cm^?1 with an infrared spectrometer.     

Isolation and determination of volatile organic sulphur compounds in aqueous solutions

Summary A procedure has been worked out for isolation and determination of volatile organic sulphur compounds in water. These compounds are isolated from an aqueous sample by countercurrent thin-layer head-space (TLHS) technique. After isolation, the sulphur compounds are burned in a quartz tube and the combustion products (SO₂/SO₃ mixture) are absorbed by a 10% solution of hydrogen peroxide. The resulting sulphuric acid is introduced into the heated part of a quartz tube, where the presence of tungsten trioxide at 1150°C ensures its complete decomposition. The sulphur dioxide formed is titrated microcoulometrically with iodine. Organic halogen compounds usually present in different waters do not interfere. The complete procedure has been tested on model solutions of sulphur compounds in the concentration range of 10–200 g S/l.     

Determination of total sulphur in fuel oils by ion chromatography

A method is described for the determination of total sulphur in fuel oils. The oils are burnt in an oxygen flask and the resulting sulphur dioxide is oxidised with hydrogen peroxide to sulphate which is subsequently determined by ion chromatography. With a 50-mg oil sample the limit of detection is 0.007% sulphur. The procedure is simple and has a r.s.d. of 2.7%. Blanks are negligible and the only interferences can be from metal ions that form insoluble sulphates. The method is compared with m.e.c.a, x.r.f. and titrimetric procedures.     

Determination of sulphur in petroleum products after sulphur dioxide generation and of sulphur dioxide in air by chemiluminescent flame emission

The determination of sulphur in petroleum products by combustion, concentration of the sulphur dioxide in sodium tetrachtoromercurate solutions and cool flame molecular emission is described. Improvements in burner design and optimization of analytical conditions result in a minimum detectable amount of 6 ng of sulphur. The absorption of sulphur dioxide from air samples and its determination by a similar method gives a detection limit of 1.3 μg SO₂ m^-3.     

In Process Citation

A simple method is described for the microdetermination of deuterium in organic compounds. It involves a flash combustion of the weighed sample in a hot empty chamber at 950-1050 degrees and swept by oxygen at 60 ml/min. Together with this combustion in the gaseous phase, an oxidation of the primary combustion gases on cupric oxide at 850 degrees is necessary. Oxidation products containing halogens and sulphur are retained on silvered alumina at 750-800 degrees . Combustion water containing deuterium oxide and hydroxide is frozen out from the combustion gases in a special trap with two five-way stop-cocks which make possible the simultaneous flow of oxygen and hydrogen; the latter is used as a carrier-gas in the apparatus from the trap downwards. The frozen water is then vaporized by heating in a hydrogen flow of 30 ml/min and reduced on magnesium at 600 degrees . Deuterium is obtained as deuterium hydride in hydrogen; it is measured versus pure hydrogen, with a thermal conductivity detector. A Determination within a series can be completed in 15 min. The precision of the results is that obtained in classical organic microanalysts.     

Simultaneous determination of nanomole amounts of sulphur dioxide and hydrogen sulphide by flow injection analysis with on-line preconcentration by means of capillary denuder tubes

A simple and rapid method for trace determination of SO2 and H2S in gaseous samples by using a flow injection system with on line preconcentration on capillary denuder is described. The gaseous samples are led through a 0.4 M sulphamic acid solution, retaining nitrogen dioxide, ammonia and hydrogen chloride. The sulphur dioxide is collected from the carrier gas stream (250 cm3 min-1) as sulphuric acid in a capillary denuder tube coated with a thin layer of 0.01-0.03 M hydrogen peroxide solution of 0.05 mM sulphuric acid; hydrogen sulphide passes into a second tube coated with 0.075 mM sodium sulphide solution of 0.1 M aqueous sodium hydroxide. The films containing the sulphuric acid and the sodium sulphide, respectively, are eluted with the corresponding circulating absorbent streams and pass through the detectors. Sulphuric acid is detected by conductimetry and sulphide is determined spectrophotometrically at 230 nm. If nanoequivalent amounts of H2S are present in the sample containing a large concentration of SO2 (SO2/H2S concentration ratio > 20), the sulphur dioxide is filtered out of the sample gas stream by solid sodium hydrogen carbonate. A limit of detection of 3.5 micrograms m-3 is obtained.     

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.     

A wet-combustion method for the determination of chlorine in coals

Chlorine in coals can be determined by wet-combustion with sulphuric acid in the presence of potassium dichromate and silver sulphate. The liberated chlorine is absorbed in hydrogen peroxide and after treatment with mercuric oxycyanide is determined acidimetrically. The method is simple, fairly rapid and should be suitable for multiplicate analysis. The results agree well with those given by two independent methods of analysis, i.e. incineration with Eschka mixture followed by the Volhard titration, and the high temperature combustion method.     

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.     

Genaue Bestimmung des Schwefels in anorganischen Schwefelverbindungen nach dem Verbrennungsverfahren

Zusammenfassung Durch Verbrennung mit Vanadiumpentoxid als Sauerstoffüberträger im Stickstoffstrom und Herabsetzung des Sauerstoffpotentials der Verbrennungsgase über metallischem Kupfer gelingt es, 99,5% des Schwefels in leicht erfaßbares Schwefeldioxid zu überführen. Für Proben mit einem Schwefelgehalt zwischen 1 und 8 mg beträgt die Standardabweichung 5,2 g.

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Precise determination of sulphur in inorganic sulphur compounds by the combustion method

Summary By combustion with vanadium pentoxide as oxidant in a nitrogen current and after reduction of the oxygen potential of the combustion gas over metallic copper, 99,5% of the total sulphur are obtained as easily detectable sulphur dioxide. The standard deviation of the method is 5.2 g for samples containing between 1 and 8 mg of sulphur.

     

Determination of traces of hydrogen in fluoro-organic compounds

The determination of traces of hydrogen in highly fluorinated compounds has been studied. Nitrogen and sulphur in the sample interfere slightly in the pyrolytic method of Miller etal. A straightforward combustion method is proposed in which the sample is burned in oxygen over magnesium oxide at 900° and the water formed is determined either gravimetrically or titrimetrically.