Direct micro determination of oxygen in organic compounds

Summary A simple procedure for the determination of oxygen has been tried with compounds containing carbon, hydrogen, and oxygen. It has the advantage that a temperature of 700° C is sufficient.

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Zusammenfassung Eine einfache Verbrennungsmethode zur Bestimmung von Sauerstoff, für die eine Temperatur von 700° C ausreicht, wurde an Verbindungen, die nur Kohlenstoff, Wasserstoff und Sauerstoff enthalten, erprobt.

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Résumé On a essayé une méthode simple pour doser l'oxygène dans des composés contenant du carbone, de l'hydrogène et de l'oxygène. Elle a l'avantage de ne pas nécessiter une température supérieure à 700° C.

     

A new method for the determination of oxygen in organic compounds

Oxygen in compounds of carbon, hydrogen, and oxygen can be determined by heating the sample with an excess of strontium oxide and graphite in. a nickel bomb or sealed Vycor glass tube. During the heating period, three hours at 650° C, the oxygen of the sample is converted to carbonate. The carbonate is then determined volumetrically. The accuracy of the method was found to be ± 0.3% (absolute percentage error) for several types of compounds. Most elements other than carbon, hydrogen, and oxygen interfere. Compounds like phenol, that are exceedingly resistant to complete pyrolysis, yield low resuilts. Carbon in organic compounds can be determined by heating the sample with barium nitrate, and subsequently determining carbonate in the mixture.     

A manometric method for the determination of oxygen in organic compounds

Summary A vacuum apparatus is described for the determination of oxygen in 3 to 5 mg of organic substance. The oxygen of the substance is converted to carbon monoxide by ignition in a bomb at 1050 to 1055° C. Corrections are calculated from thermodynamic data for the amounts of water and carbon dioxide not reacting at the ignition temperature.

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Zusammenfassung Eine Vakuumapparatur für die Bestimmung des Sauerstoffes in 3 bis 5 mg organischer Substanz wird beschrieben. Der in der Substanz enthaltene Sauerstoff wird durch Erhitzen auf 1050 bis 1055° C in einem geschlossenem Quarzrohr in Kohlenmonoxid übergeführt, das dann in der Vakuumapparatur zu Kohlendioxid oxydiert und durch Absorption gemessen wird. Korrekturen werden aus thermodynamischen Daten für die bei der Verbrennungstemperatur nicht reagierenden Wasser- und Kohlendioxidmengen berechnet.

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Résumé On décrit un appareil á vide pour le dosage de l'oxygéne sur 3 á 5 mg de substance organique. On convertit l'oxygéne de la substance en oxyde de carbone par combustion dans une bombe, á 1050–1055° C. On calcule les corrections á partir des données thermodynamiques pour l'eau et le gaz carbonique qui ne réagissent pas á cette température.

     

A rapid method for the determination of organic carbon in soil

TIURIN'S method for the determination of organic carbon in soil is modified to give results practically identical with those of the dry combustion method. The standard deviation of a single determination is only 12%. By using 50 mg of soil and 10 ml of 0.2 N dichromate solution, soils with a carbon, content up to 12% can bo analysed. The method is suitable for all soils except those containing much chloride or reducing substances other than organic carbon Carbonates do not interfere.     

Influence of carbon dioxide in the determination of oxygen in copper by reduction fusion

It has been reported that copper melted in a graphite crucible at high temperature will give off its oxygen content mainly as CO and partially as CO(2). Thus if oxygen in copper is determined by means of apparatus designed to measure only CO as the reaction product, the results are obviously liable to error. Methods of suppressing formation of CO(2) during the fusion process are proposed. When the oxygen is determined by gas chromatography, formation of CO(2) can be suppressed by adding a 0.5% Si-1.5% NiCu bath-alloy together with the copper sample or by inserting a spectrographically pure carbon rod into the graphite crucible used for the fusion. When the oxygen is determined by coulometry, formation of CO(2) can be suppressed by the addition of the SiNiCu bath-alloy or by appropriate modification of the graphite crucible to obtain an optimum working temperature. The results obtained by either method are in agreement with those obtained by a modified vacuum fusion method in which CO and CO(2) can both be measured. These methods have been validated by analysis of two standard reference materials.     

A convenient isotopic dilution method for the direct determination of oxygen in fluorinated organic materials

Summary A method is described for the microdetermination of oxygen in fluorinated organic compounds. The unknown material is pyrolyzed together with¹⁸O-containing succinic acid, in a sealed, evacuated, specially-purified copper tube. After equilibration at 850°C, the tube is punctured and the pyrolysis gases are admitted to a mass spectrometer. Comparison of the m/e-46/44 ratio (C¹⁶O¹⁸O/C¹⁶O¹⁶O) to the ratio obtained from similar pyrolysis of the oxygen-18 compound only, provides a means of calculating the oxygen content of the unknown.The copper tubes are made from ordinary, rigid, 1/4 o. d. tubing, which is purified by reduction in hydrogen and heating under vacuum. They are sealed by induction welding.The procedure has been used successfully for a variety of fluorinated compounds including several metal salts of fluorinated acids.

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Zusammenfassung Eine Methode für die Mikrobestimmung von Sauerstoff in fluorhaltigen organischen Verbindungen wurde beschrieben. Das Untersuchungsmaterial wird mit¹⁸O-markierter Bernsteinsäure in einem evakuierten, verschlossenen, besonders gereinigten Kupferrohr pyrolysiert. Nach Gleichgewichtsemstellung bei 850° C wird dieses Rohr punktiert und die Pyrolysegase in ein Massenspektrometer geleitet. Der Vergleich des m/e-46/44-Verhältnisses (C¹⁶O¹⁸O/ C¹⁶O₂) mit dem nach Pyrolyse der¹⁸O-markierten Verbindung allein bietet die Möglichkeit, den Sauerstoffgehalt der Probe zu berechnen.Die Kupferrohre werden aus gewöhnlichem, hartem Rohrmaterial mit 1/4 Zoll äußerem Durchmesser hergestellt, mit Wasserstoff reduziert, im Vakuum erhitzt und schließlich durch Induktion verschweißt.Das Verfahren wurde erfolgreich zur Analyse verschiedener fluorhaltiger Verbindungen einschließlich Metallsalzen fluorhaltiger Säuren verwendet.

     

A simple routine method for the rapid determination of organic and inorganic carbon in oil shale

A procedure for the rapid determination of organic and inorganic carbon in oil shale samples is proposed. Oil shale samples are decomposed in an oxygen stream at three different temperatures (450°C, 550°C, 900°C). The resulting CO₂ is determined after absorption in 0.02 M NaOH in a relative conductometric detection unit. Temperature. differentiated carbon analysis was used to establish the decomposition temperatures of the organic material (450°C) and the inorganic fractions (550°C and 900°C). The method was tested for samples weighing 2–4 mg. Oil shales with organic carbon contents of 8–20% were determined with good reproducibility (r.s.d. 0.4–1.3%). The accuracy was tested with a standard oil shale sample. One determination requires 8 min.     

Automatic coulometric method for the determination of carbon and hydrogen in organic substances

Conclusions A coulometric method is proposed for the microdetermination of carbon and hydrogen in organic substances.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 700–701, March, 1972.     

A rapid automatic method for the determination of oxygen in organic substances, using coulometry at controlled potential

An Unterzaucher apparatus for the determination of oxygen in organic compounds is used. The iodine vapour formed in the anhydroiodic acid tube is led by a stream of nitrogen to the cathodic chamber of an electrolysis cell. Here the iodine is reduced at controlled potential at a rotating Pt-eiectrode. The amount of electricity used is determined by an electronic integrator and read from a digital voltmeter. For weights of samples in the range 0.5-6 mg the standard deviation is about 0.08% oxygen.     

A method for the determination of phosphorus in organic compounds

The sample is decomposed by heating with nitric and sulphuric acids, the nitric acid is completely removed, and phosphomolybdic acid is formed under carefully controlled conditions of acidity and reduced to molybdenum blue by means of ferrous ammonium sulphate. The colour intensity is measured spectrophotometrically.     

Platinum free ternary electrocatalysts prepared via organic colloidal method for oxygen reduction

Novel ternary palladium based alloy catalysts, PdFeIr/C, for oxygen reduction reaction (ORR) have been successfully prepared via an organic colloid method with ethylene glycol as solvent and sodium citrate as complexing agent. The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX). Electrochemical activity of the catalysts for ORR was evaluated by steady state polarization measurements, which were carried out on an ultra thin layer rotating disk electrode (RDE). Compared to pure Pd/C and Pd₃Fe/C, results showed that the ORR activity of PdFeIr/C was highest, and its methanol tolerance was better than Pt/C catalyst.     

Catalysts for the determination of oxygen in organic compounds

Summary Thermal decomposition of metal-organic complexes of nickel, cobalt and iron has given catalysts which are very effective at about 900° for the conversion of carbon dioxide, water and other oxygencontaining sample decomposition products to carbon monoxide in the direct determination of oxygen in organic compounds when using a modified Unterzaucher type apparatus. A copper catalyst similarly prepared required a temperature of 1030° whereas a manganese complex decomposition product was ineffective.

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Katalysatoren zur Sauerstoffbestimmung in organischen Substanzen

Zusammenfassung Durch thermische Zersetzung metallorganischer Komplexe von Ni, Co und Fe erhält man Katalysatoren, die die Umwandlung von CO₂, H₂O und anderen sauerstoffhältigen Zerfallsprodukten zu CO bei etwa 900° C bei der direkten Sauerstoffbestimmung in einer modifizierten Unterzaucher-Apparatur sehr wirksam fördern. Ein ähnlich hergestellter Cu-Katalysator erfordert 1030° C und das Zersetzungsprodukt eines Mn-Komplexes ist unwirksam.

     

Studies on oxygen determination in organic microanalysis. I. A modified purification method of nitrogen gas

Summary Reduced copper has been used generally for removing the oxygen in the nitrogen gas in the microdetermination of oxygen, but instead of reduced copper the authors have used about 20 g of Raney-nickel in the dry state prepared through the development of Raney-alloy, and have found that the oxygen is removed completely from the nitrogen gas at room temperature; Raney-nickel has also a much greater capacity than the reduced copper.

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Zusammenfassung Zur Reinigung des für die Mikrobestimmung des Sauerstoffs verwendeten Stickstoffs wurde üblicherweise reduziertes Kupfer verwendet. An dessen Stelle verwenden die Verfasser etwa 20 g trockenes Raney-Nickel und konnten feststellen, daß der Stickstoff damit schon bei Zimmertemperatur vollständig von Sauerstoff befreit wird. Außerdem hat Raney-Nickel eine viel höhere Kapazität als reduziertes Kupfer.

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Résumé On emploie en général le cuivre réduit pour l'élimination de l'oxygène contenu dans l'azote lors du microdosage de l'oxygène; au lieu de ce réactif les auteurs ont employé environ 20 g de nickel de Raney, à l'état sec préparé à partir d'alliage de Raney; ils ont trouvé que l'oxygène était éliminé complètement de l'azote à la température ambiante; le nickel de Raney a également une capacité d'absorption beaucoup plus grande que le cuivre réduit.

     

A compleximetric method for the determination of dissolved oxygen in water

A new method is proposed for the determination of dissolved oxygen in water. The iron(III) formed from FES at pH 7.5 is titrated with EDTA solution in presence of salicylic acid indicator after adjustment of the pH to about 2.4 The method is slightly less precise than the Winkler method for pure waters but more accurate for polluted waters; it is simple and convenient for field use.