Some important moments in the development of organic elementary analysis

As early as 1784, Lavoisier carried out combustions of organic substances in a glass bell-jar filled with oxygen. No quantitative results were however obtained. In 1810, Gay-Lussac and Thenard burned organic material in a vertical tube with potassium chlorate as oxidizing agent, and analyzed the resulting mixture of gases. Later (1814–1817), Berzelius used a horizontal tube and a mixture of potassium chlorate and sodium chloride, and weighed the water and carbon dioxide formed. In 1831, Liebig described his potash apparatus and created a general method for the analysis of organic substances, in which cupric oxide was the oxidizing agent. The most important advance in organic analysis after LIEBIG is due to Pregl (1912). By his very well known methods of micro-analysis, progress in organic chemistry has been stimulated enormously. The volumetric determination of nitrogen suggested by Dumas in 1833, was developed by Pregl into a micro-method.     

Emich's contribution to qualitative organic elementary microanalysis

Summary UsingEmich's classical capillary technique, a simple scheme has been devised for the detection of the elements most frequently occurring in organic compounds.

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Zusammenfassung Emichs Arbeitsweise im ausgezogenen Röhrchen erlaubt den Nachweis der in organischen Verbindungen am häufigsten vorkommenden Elemente.

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Resumen Aplicaciön de technica capilar clasica deEmich résulta en la evolución de una sistema simple para la detección de los elementos mas frequentamente encontrados en compuestos organicos.

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Résumé En utilisant la technique classique du capillaire d'Emich, on a imaginé une méthode de détection simple des éléments que l'on rencontre le plus fréquemment dans les composés organiques.

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Retired, formerly with New York University, New York City, U. S. A.

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Retired, formerly with the University of Buenos Aires, Buenos Aires, Argentina.

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On the occasion of the hundredth return ofFriedrich Emich's birthday.     

An experimental analysis of coal aluminium mixture in coal fired furnace

Coal is an important fuel used in boiler furnaces. There are problems like unburnt coal and solid wastes like ash contain arsenic, selenium, chromium and cadmium while using it. In order to avoid all such difficulties, aluminium metal powder in various grain sizes mixed with pulverized coal and burned. aluminium metal powder is one of the pyrotechnics having higher calorific value and low ignition temperature. The thermal behavior of aluminium powder along with coal is recorded in DTA. The collected ashes were tested in Scanning Electron Microscope and X-Ray Diffraction meter. The SEM results show that coal ash is having granular and regular structure. All the particles have a size range from 5 to 8 μm. On the other hand, the aluminium coal mixture ash shows a fibrous matrix and the particles are irregular. In XRD graph, the peaks in the graph show orientation of atoms in particular plane and angle. The coal ash has a lot of peaks, but the maximum count value reaches only to 340.97. However the value of counts reaches a maximum of 1,539.06 for aluminium ash. This denotes high atom orientation in a single lattice plane.     

Sodium dispersions in elementary analysis

Summary Gently warming the compound with a dispersion of sodium in a suitable organic solvent reduces nitrogen to ammonia and sulfur, to sulfide.

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Zusammenfassung Stickstoff wird zu Ammoniak und Schwefel zu Sulfid reduziert, wenn die organische Verbindung vorsichtig mit einer Dispersion von metallischem Natrium in einem geeigneten organischen Lösungsmittel erwärmt wird.

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Résumé En chauffant doucement le composé avec une dispersion de sodium dans un solvant organique convenable, l'azote est réduit en ammoniac et le soufre en sulfure.

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On the occasion of the hundredth return ofFriedrich Emich's birthday.     

The L'vov platform for furnace atomic absorption analysis

The L'vov Platform converts the Massmann-type graphite furnace into a furnace that provides a constant temperature environment for the more volatile metals. A very great reduction of matrix interferences for Pb, Cd and Tl is reported, so long as the matrix concentration provides a background signal during atomization that is small enough to be controlled by the deuterium arc background corrector. Interferences for Cu, Mn and Sn are also reduced to some extent. L'vov's recent theory relating to vapor phase thermodynamics makes it possible to predict both qualitatively and semi-quantitatively many of the remaining interference effects. This provides potential solutions to remaining problems which are herein explored. The continued test of interferences reported in the literature indicates that most are not present in the modern furnaces when they are used in an optimum manner.     

An analysis of elementary processes of water desorption from zeolites of type a

Complex DSC curves of water desorption from LiA, NaA and KA zeolites were resolved into the most probable elementary curves. The activation energies and transition temperatures of corresponding elementary processes were determined. On the basis of the results obtained a model is proposed for water binding to M⁺ A^? zeolites with three different phases.     

An anion-exchange high-performance liquid chromatography method coupled to total organic carbon determination for the analysis of water-soluble organic aerosols

The chemical composition of water-soluble organic carbon (WSOC) in atmospheric aerosol particles is largely unexplored, due to the myriad of individual compounds, which has hampered attempts to attain a full characterization at the molecular level. An alternative approach, focusing on the analysis of a few main chemical classes, allowed the quantitative fractionation of WSOC into neutral compounds (NC), mono- and di-acids (MDA) and polyacids (PA) through an anion-exchange liquid chromatographic method. Previous attempts to quantify NC, MDA and PA relied on a low-pressure chromatographic technique using a volatile buffer, followed by total organic carbon (TOC) analysis of the fractions, or alternatively on a faster HPLC-UV method which provided a quantification of the fractions based on empirical relationships between UV signal and TOC concentration. Here, we report an upgraded anion-exchange HPLC technique, allowing direct TOC analysis of the eluted fractions, without any pre-treatment, thus permitting a great simplification of quantitative analysis and preventing sample losses. The new HPLC-TOC methodology, employing completely inorganic eluents shows the same efficiency of the former HPLC-UV method employing organic additives, with the exception of phenolic compounds, which are retained on the column by secondary interactions, and low-molecular weight tricarboxylic acids, which are recovered among MDA. The new anion-exchange liquid chromatographic method can recover a substantial amount (86-100%) of water-soluble organic carbon from atmospheric aerosol extracts, thus allowing a higher retention and fractionation capacity with respect to alternative techniques, like solid phase extraction.     

The mechanism of the reaction of elementary astatine with organic solvents

The mechanism of the reaction of elementary astatine with benzene, toluene and monochlorobenzene were studied by means of radiogaschromatography. The reaction proceeds in two steps with benzene and toluene. In Step 1 the chemical bond of At₂ is cleaved by the disintegration of either astatine and the remained astatine reacts immediately with solvent. At Step 2 the compound produced at Step 1 is started to decompose by the decay of astatine. But this mechanism could not be applied to the astatine-monochlorobenzene system.     

An evaluation of solid-phase microextraction for analysis of volatile organic compounds in drinking water

Solid-phase microextraction (SPME) has been applied to the quantitative analysis of 60 volatile organic compounds (VOCs) in drinking water. Equilibration curves for the partitioning of the VOCs between the fiber coating and fortified water obtained at 20, 50, and 80 °C are found between the theoretical curves for completely agitated and non-agitated samples. Two important factors for the amount adsorbed by the SPME fiber coating are the extraction time and the fiber coating/water distribution coefficient, K_FW . Both depend on the sample temperature, but in a counteracting manner: Increasing the temperature shortened the equilibration times, especially for the heavier VOCs, but also lead to lower K_FW values, and consequently a lower sensitivity of the method. K_FW values are determined for 33 of the VOCs at 40, 60, and 80°C and the heats of adsorption,–ΔH, are calculated. The nature of the adsorption is found to be exothermic which explains the decreasing sensitivity of the method with increasing temperature. Detection limits were typically from 20 ng/l to 200 ng/l, except for the very light VOCs with which detection difficulties were encountered. For all of the VOCs the linear range extended from the lowest concentration at which they were actually detected to at least 5 mg/l. The precision, 3% average standard deviation when an internal standard was used, was satisfactory for most quantitative routine analysis. SPME was also applied to head-space (HS) analysis of drinking water through the coupled equilibrium between water/head-space/fiber coating. HS-SPME is demonstrated to have shorter equilibration times than SPME directly from the water and equal sensitivities, except for the very light VOCs. Water samples from a drinking water plant contaminated in the low μg/l range with 1,1,1-trichloroethane, trichloroethene and tetrachloroethene were analyzed. There seems to be a reasonable agreement between results obtained by SPME and purge & trap. It is concluded that SPME has a great potential for drinking water analysis.     

Enthalpies of elementary chain propagation steps in the oxidation of organic compounds

A calculation of the enthalpies of elementary steps of the intra- and intermolecular chain propagation for model oxidation reactions of ethers, esters, ketones and hydrocarbons has been carried out. The heats of the intermolecular and intramolecular transfer of free valence with participation of peroxy radicals and C−H bond of the oxygen-containing compounds are shown to be comparable.     

An organic p-type dopant with high thermal stability for an organic semiconductor

To overcome the thermal instability of a p-doped organic hole transporting layer using the state-of-the-art p-type dopant, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane, a potent electron accepter, 3,6-difluoro-2,5,7,7,8,8-hexacyanoquinodimethane, has been found to possess superior thermal stability and proved to be an excellent p-type dopant.     

An elementary method for calculating orientation-averaged fully differential electron-impact ionization cross sections for molecules

Currently there are no reliable theoretical approaches for calculating fully differential cross sections (FDCS) for low-energy electron-impact ionization of large molecules. We have recently introduced the distorted-wave impulse approximation as a first step in developing improved theoretical approaches. One significant obstacle to evaluating improved theoretical approaches which require significant computer resources lies in the fact that the existing experimental data require taking averages over all molecular orientations. To circumvent this problem, it has been proposed to approximate the orientation-average by using an orientation-averaged molecular orbital in the calculation of the FDCS. The theoretical justification and expected range of validity for the approximation is given in this paper. Examples are presented for electron-impact ionization of H(2) and N(2).