Microdetermination of oxygen in organic compounds using a glassy carbon pyrolysis tube and nondispersive infrared detection

A glassy carbon pyrolysis tube holding a filling of carbon granules, protected from atmospheric oxygen by the carrier gas and an aluminum oxide ceramic mantle tube, has been successfully used for the first time in the microdetermination of oxygen. The reaction temperature of 1300 °C assures the quantitative transformation of oxygen to carbon monoxide, which is measured by infrared detection. The analysis of fluorine, phosphorus and alkali metal containing compounds is now possible. A 10% hydrogen content in the nitrogen carrier gas enhances liberation of oxygen in organometallic compounds. The method is applicable to sample weights between 0.1 and 5 mg and the time required for one analysis is 100 s.     

Microdetermination of oxygen at traces level in organic sulfur compounds

We have described an original method allowing us to determine traces of oxygen in organic compounds such as polymers modified through grafting of functions containing oxygen.The method allows us to obtain oxygen contents included between a few hundred ppm and 7 to 8%. It consists in the pyrolysis of the sample, the reduction of oxygen to carbon monoxide and, finally the detection of the latter in an infrared analyzer.     

Analysis of gases containing inorganic and organic compounds using a combination of a thick-film capillary column and a packed adsorption column

A gas chromatographic system consisting of one multiport valve, two (hot-wire and flame-ionization) detectors and two analytical columns (one thick-film capillary and one packed adsorption column) is used for the analysis of gas samples containing a number of inorganic compounds (hydrogen, argon, oxygen, nitrogen, carbon monoxide, and carbon dioxide) and organic compounds. Examples include samples containing hydrocarbons up to n-nonane and benzene and toluene. The system also permits the analysis of more complicated samples containing, for example, alcohols, in addition to hydrocarbons.     

Selective oxidation surface analysis on metals and minerals

Selective Oxidation Surface Analysis (SOSA) studies were made on (a) metal surfaces containing high molecular weight carbonaceous impurities (i.e. greases, oils) and (b) mineral particles containing adsorbed “surfactant collectors”.The principle of the technique consists of heating the sample in a stream of oxygen. The surface carbon species are selectively oxidized over characteristic temperature ranges and the effluent gas fed over a catalyst. The resulting carbon dioxide was continuously analyzed by an I.R. detection system. The method was shown to capable of differentiating and quantifying the various carbonaceous compounds.SOSA could prove useful in the mineral and metallurgical industries.     

Paradigms and paradoxes: organic thermochemistry without hydrogen: carbon oxides and nitrides

All organic compounds contain carbon. Most contain hydrogen. This brief study discusses the enthalpy of formation of a collection of organic compounds containing only oxygen or nitrogen accompanying the carbon.     

Automation in organic analysis II. Simultaneous microdetermination of oxygen and nitrogen

A simple, rapid, and accurate method of simultaneous determination of oxygen and nitrogen in organic compounds, containing (in addition to C, H, and O) Cl, Br, and I, is described. The principle of the method consists in the pyrolytic decomposition of the analyzed compound in a current of hydrogen at 1000–1100 °C and the conducting of the hydropyrolytic product through layers of nickel and platinized carbon (50% Pt) heated at 1050 °C. On this filling the nitrogen-containing products are transformed to elementary nitrogen, the oxygen-containing products are transformed to carbon monoxide, the halogens to hydrohalogenides, and methane is decomposed. After removing hydrohalogenides by soda asbestos, carbon monoxide and nitrogen are separated on a chromatographic column filled with Porapak Q, and determined with a catharometer. The whole analysis, including the weighing of the sample, requires 25 min. Sulfur interferes with the determination.     

Simultaneous determination of oxygen and cadmium in cadmium and cadmium compounds

Cadmium and its compounds were analysed for oxygen and cadmium by a modification of the Schütze-Unterzaucher method. Oxygen in some compounds such as cadmium oxide, nitrate and sulphate could not be determined by the usual method. The method of adding carbon was employed for the determination of total oxygen. Total oxygen could be determined by the addition of 5 mg of carbon to a sample boat and heating at 950 degrees . The determination was also carried out by addition of naphthalene (2 mg). It was found that the cadmium powder and cadmium flake used contained ca. 1 and 0.15% oxygen, respectively. Oxygen and cadmium in cadmium and its compounds were simultaneously determined by the addition of 2 mg of naphthalene. Cadmium was determined colorimetrically by use of glyoxal-bis-(2-hydroxyanil). Oxygen and cadmium in the samples could be determined simultaneously with an average error of -0.02 and -0.22%, respectively.     

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.     

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.     

氮氧自由基的应用研究进展

氮氧自由基化合物是指含碳、氮、氧、氢等元素以及自旋单电子的有机化合物,因其自身的特殊性质被广泛应用于很多领域。本文结合氮氧自由基的特点,对其在生物学、磁性、有机催化和阻聚等方面的应用研究进行了总结,并对氮氧自由基化合物的发展趋势进行了展望。     

Approaches to Total Synthesis of Heterocyclic Steroidal Systems

In heterocyclic steroids the carbon atoms of the steroid skeleton (positions I to 17) are replaced in part by hetero atoms. The term generally denotes compounds containing one or two nitrogen, oxygen, and/or sulfur atoms. The part of the molecule containing the hetero atom is either introduced as a preformed unit or is constructed by stepwise synthesis. The examples given in the present article contain the hetero atoms in ring A, ring B, between rings A and B, and/or between rings C and D.     

Method d'estimation des limites d'inflammabilite

We have employed the criteria defined by the CHETAH (ASTM) program to predict the lower and the upper flammability limits of various organic compounds. The results obtained for molecules containing carbon, hydrogen, oxygen and nitrogen are, in most cases, in good agreement with experimental values. The difficulties encountered when the molecule contains a heteroatom can be overcome by knowledge of the stoichiometric conditions of the combustion reactions.     

Nickel and cobalt hexamethylentetramine complexes (NO3)2Me(H2O)6(HMTA)2.4H2O (Me = Co2+, Ni2+): new molecular precursors for the preparation of metal dispersions

Nickel and cobalt hexamethylenetetramine (HMTA) complexes (NO3)2Me(H2O)6(HMTA)2.4H2O were prepared and characterized structurally by single-crystal X-ray diffraction. Both compounds crystallize in the triclinic P1 space group with the same structure. The structures are three-dimensional hydrogen-bonded supramolecular frameworks containing two-dimensional cationic assemblies connected with proton acceptors, which are noncoordinated anionic species (nitrate) and neutral HMTA molecules. Thermal decomposition of these compounds under an inert atmosphere leads to the high-surface-area metal-carbon foams containing nickel and cobalt nanoparticles embedded within onionlike carbon shells. The decomposition process as studied by thermal analysis and in situ X-ray absorption spectroscopy (XAS) measurements occurs as a rapid loss of oxygen in the form of CO, beginning at temperatures as low as 323 K. As the in situ XAS study demonstrated, the evolution of nickel and cobalt coordination spheres occurs with intermediate formation of amorphous metal carbides, which subsequently decompose to the metal nanoparticles covered with carbon shells.     

The simultaneous determination of carbon and oxygen in semiconductor silicon by helium-3 activation analysis

A non-destructive method for the simultaneous determination of carbon and oxygen in silicon by helium-3 activation analysis is described. The determination is based on a simplified standardization method. The method was applied to samples containing 0.05–3 p.p.m. of carbon and 0.05–10 p.p.m. of oxygen. The determination limit of carbon varies from 30 to 300 p.p.b. depending on the oxygen concentration.     

一氧化碳和甲烷在微波等离子体下直接转化成低碳烃(英文)

本文报道了微波等离子体下（２．４５ＧＨｚ）一氧化碳和甲烷直接转化成低碳烃的一种新方法。研究了影响产物分布的几个因素：微波输入功率、反应物比例及体系压力。乙炔和乙烷是主要有机产物。随着微波输入功率的增加和体系压力或ＣＨ４／ＣＯ比例的降低，乙炔含量增加，乙烷含量减少。反应中有少量乙烯和Ｃ３烃生成。没有检测到Ｃ４及含氧有机化合物。     

The radiation yields of radicals in solid organic substances containing heteroatoms

EPR has been used to measure the radiation yields of radicals (G_R) in various classes of organic compounds containing heteroatoms: dialkyl disulfides, diphenyl- and dibenzyl disulfide, alkyl derivatives of thiophene, thiophenecarboxylic acids, halogen derivatives of thiophene, and saturated heterocyclic compounds containing nitrogen, oxygen, and sulfur atoms. It has been shown that 1) G_R=0.2–1 per 100 eV in saturated disulfides and cyclic sulfides, while G_R=3–8 per 100 eV in the corresponding hydrocarbons, alcohols, oxides, and alkyleneimines; 2) the introduction of a sulfur atom into aromatic compounds does not alter the radiation stability; 3) disturbance of the conjugation of halogen atoms and of the carboxyl group with the thiophene ring leads to a decrease in the radiation stability. It is suggested that the increased stability of sulfur-containing compounds may be due to the excitation of the electrons in the S atom at the d-orbitals, which lie appreciably lower in the sulfur atom than in the atoms of oxygen, nitrogen, and carbon, and the subsequent dissipation of the excitation energy.     

Energetic nitrogen-rich salts and ionic liquids

Energetic salts offer many advantages over conventional energetic molecular compounds. The use of nitrogen containing anions and cations contributes to high heats of formations and high densities. Their low carbon and hydrogen content gives rise to a good oxygen balance. The decomposition of these compounds is predominantly through the generation of dinitrogen which makes them very promising candidates for highly energetic materials for industrial or military applications.     

Surface activity and fluorite flotation with myristic acid derivatives containing oxygen and sulphur atoms

Surface tension isotherms and fluorite flotation were studied in systems containing myristic acid derivatives in which carbon atoms in the hydrocarbon skeleton were partly replaced by oxygen and/or sulphur atoms. The location of the oxygen and sulphur atoms affects significantly compound hydrophobicity, adsorption at the air/water interface and fluorite flotation. The most effective collectors were the compounds with one oxygen or sulphur atom close to the carboxylic group.     

Analysis of complex industrial samples by gas chromatography; a report on selected past activities

Summary A review of past activities concerning selected industrial analytical problems is given. This includes the following question: preparation of pure gas mixtures to be used for calibration, catalytic conversion of ester and pyridin samples to carbon dioxide and a one-point calibration method using peak heights, both for quantitative analysis, analysis of gas mixtures containing fluorine and inorganic fluorine compounds and the determination of the oxygen and fluorine content of the sample, separation and identification of hydrocarbons in shale oil and petroleum fraction samples, and analysis of wine.     

Developing a methodology for carbon isotope analysis of lacustrine diatoms

Stable isotope analysis of sedimentary carbon in lakes can help reveal changes in terrestrial and aquatic carbon cycles. A method based on a single, photosynthetic organism, where host effects are minimised, should offer more precision than carbon isotope studies of bulk lake sediments. Here we report the development of a systematic method for use on fossil lacustrine diatom frustules, adapted from previous studies in marine environments. A step-wise cleaning experiment on diatomaceous lake sediments from Lake Challa, near Mount Kilimanjaro, was made to demonstrate the necessary treatment stages to remove external sedimentary carbon. Changes in soluble carbon compounds during these cleaning experiments were measured using gas chromatography/mass spectrometry (GC/MS). The mass spectrometry methods were refined to measure the small percentage of carbon in these samples and details of these methods are presented. Samples of cleaned diatoms containing <1% carbon yielded robust results. Carbon isotope analyses of diatom samples containing different species mixtures were performed and suggested that differences existed, although the effects lay within current experimental error and require further work. Unlike what was found in work on oxygen and silicon isotopes from diatom frustules, mineral contamination had no discernible impact on the diatom carbon isotope ratios from these sediments. The range of values found in the lakes investigated thus far can be interpreted with reference to the supply and nature of carbon from the catchment as well as to the demand generated from lake primary productivity.