The semi-micro determination of fluorine,chlorine, and nitrogen in organic compounds

The organic compounds are fused with sodium in a nickel bomb in the usual way and the fluoride, chloride, and cyanide ions produced are determined. The method cannot be used to determine nitrogen in organic compounds containing oxygen since, in such cases, some of the nitrogen is converted to cyanate ion.     

Micro and semi-micro determination of organic nitrogen by use of potassium bromate

After Kjeldahl digestion of an organic compound, nitrogen is determined by oxidation of the resultant ammonium sulphate with hypobromite produced in situ by the addition of an excess of potassium bromate and bromide in a special flask. The unreacted potassium bromate is determined iodometrically.     

Gravimetric semi-micro determination of sulphur in organic compounds containing phosphorus

Summary A semi-micro method is described for the determination of sulphur in organic compounds. The sample is burned by the oxygen flask method. After the combustion products are absorbed, the sulphur content is determined gravimetrically as barium sulphate. By increasing the acidity of the solution to 0.20–0.25N in hydrochloric acid, the sulphur content can be determined with the same precision in samples which also contain phosphorus.

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Zusammenfassung Eine Halbmikromethode zur Bestimmung des Schwefelgehaltes in organischen Verbindungen wurde beschrieben. Die Substanz wird nachSchöniger in einem 500-ml-Kolben verbrannt. Nach Absorption der Verbrennungsprodukte wird das Sulfat mit Bariumchlorid gefällt und gewogen. Durch Erhöhung der Salzsäurekonzentration auf 0,20 bis 0,25 Val pro Liter kann der Schwefelgehalt auch in Phosphor enthaltenden Proben mit gleicher Genauigkeit bestimmt werden.

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Résumé On décrit une méthode semi-micro pour le dosage du soufre dans les composés organiques. On brûle l'échantillon suivant la méthode de la fiole à oxygène. Après absorption des produits de combustion, on détermine la teneur en soufre par gravimétrie à l'état de sulfate de baryum. En augmentant l'acidité de la solution jusqu'à 0,20–0,25N dans l'acide chlorhydrique, on peut déterminer la teneur en soufre avec la même précision dans les échantillons contenant également du phosphore.

     

Fluorinated heterocyclic compounds: Selective chlorine/fluorine exchange reactions on pyrimidines

Selective chlorine/fluorine exchange reactions on tetrachloropyrimidine, 6-methyl-, 6-chloromethyl-, 6-dichloromethyl-, and 6-trichloromethyl-2,4,5-trichloropyrimidine are described. Sodium fluoride, potassium fluoride, hydrogen fluoride, and antimony trifluoride were used as the fluorinating agents. It was found that NaF and KF fluorinate only in the heterocyclic nucleus, HF in the nucleus and in the chlorinated methyl group, and SbF₃ only in the chlorinated methyl group. In the first stage of fluorination with NaF only chlorine bound in position 4 of the pyrimidine ring is exchanged. The HF reaction is an equilibrium reaction in which the substitution of the fluorine for the first chlorine atom occurs preferentially in position 2. The behaviour of partly fluorinated pyrimidines in nucleophilic exchange reactions is also discussed.     

Micro determination of chlorine or bromine in organic compounds

Summary Attention is drawn to a method recently described byCheng for the rapid micro determination of chlorine or bromine in organic compounds, which the present author feels is worthy of wide acceptance because of its rapidity, simplicity and accuracy.The organic compound is burnt in oxygen by the Schöniger flask technique, the halogen absorbed in alkaline peroxide and the resultant halide determined by titration with mercuric nitrate solution using diphenylcarbazone as indicator, the titration being carried out in an aqueous ethanol solution after adjusting the apparent pn value to 3.6.The titration procedure has been investigated with regard to the effect of p_H, and of sulphate, phosphate and fluoride ions, and means of overcoming any interference from these ions are described.

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Zusammenfassung Es wird auf die kürzlich vonCheng veröffentlichte Mikro-Schnell-bestimmungsmethode für Chlor oder Brom in organischen Verbindungen hingewiesen, die der Verfasser wegen ihrer Schnelligkeit, Einfachheit und Genauigkeit für allgemein verwendbar hält.Die organische Substanz wird nach der Flaschenmethode vonSchöniger verbrannt, das Halogen in alkalischer Peroxydlösung absorbiert und das Halogenid mit Quecksilber(II)-nitratlösung und Diphenylcarbazon als Indikator titriert. Die Titration wird in wäßriger Äthanollösung bei einem scheinbaren p_H von 3,6 ausgeführt.Der Einfluß des p_H, der Sulfat-, Phosphat- und Fluoridionen auf den Titrationsvorgang wurde untersucht und Wege zur Ausschaltung etwaiger Störungen durch diese Ionen angegeben.

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Résumé On attire l'attention sur une méthode récemment décrite parCheng, pour le microdosage rapide du chlore et du brome dans les composés organiques, et que cet auteur estime digne d'être largement utilisée en raison de sa rapidité, de sa simplicité et de sa précision.Le composé organique est brûlé dans l'oxygène suivant la technique de la fiole deSchöniger, l'halogène absorbé dans un peroxyde alcalin et l'halogénure résultant dosé par titrage avec une solution de nitrate mercurique en utilisant la diphénylcarbazone comme indicateur, le titrage étant effectué en solution hydro-alcoolique après avoir ajusté la valeur du p_H à 3,6.On a examiné le procédé de titrage en considérant l'effet du p_H et des ions sulfates, phosphates et fluorures et l'on a décrit des moyens d'éviter les interférences produites par ces ions.

     

The determination of tin,chlorine, and fluorine in six japanese sedimentary standards

Concentrations of tin, chlorine, and fluorine in six new Geological Survey of Japan (GSJ) sedimentary standards are reported. Tin was determined using graphite furnace atomic absorption spectrometry (GFAAS), following a lithium metaborate (LMB) fusion of the rock material. Chlorine and fluorine were determined using ion-selective electrode (ISE) potentiometry following an acid digestion and a LMB fusion, respectively. The methods employed are briefly described and determination limits in the rock of 0.2 g/g for tin, 10 g/g for chlorine, and 100 g/g for fluorine are reported. The precision obtained for the six sedimentary standards, expressed as %relative standard deviation, averaged 5.3% over the range of 2-200 g/g tin, 5.8% over the range of 20–65 g/g chloride, and 1.7% over the range of 100–4500 g/g fluoride, all in the rock. This compares favorably to the precision obtained for international geologic reference materials determined concurrently with the GSJ sedimentary standards. The values of tin, chloride, and fluoride obtained for the international reference materials were in favorable agreement with the recommended literature values.     

The potentiometric determination of chlorine in organic compounds at the milligram and decimilligram level

Summary A rapid procedure for chlorine in milligram samples by a method combining thePregl microcombustion and theNorthrop potentiometric titration is described. Accuracy and precision are reported for 5 determinations on each of four test samples. Similar data are given for three water-soluble organic hydrochlorides where only the potentiometric titration part of the procedure is involved.A decimilligram procedure by the combinedPregl-Northrop techniques at the 0.3-mg level and theNorthrop titration for the decimilligram analysis of water-soluble organic hydrochlorides is described.

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Zusammenfassung Ein Schnellverfahren zur Chlorbestimmung in Milligramm-Einwaagen wird beschrieben, wobei die Substanz nachPregl verbrannt und das Chlor nachNorthrop potentiometrisch titriert wird. Genauigkeit und Verlä\lichkeit der Methode wurden an 4 Testsubstanzen mit je 5 Bestimmungen geprüft. Au\erdem werden Beleganalysen für die unmittelbare potentiometrische Bestimmung des Chlors in drei wasserlöslichen organischen Chlorhydraten angeführt. Analoge Verfahren werden für die Chlorbestimmung in Dezimilligrammproben beschrieben. Bei Kombination der Verbrennung mit der potentiometrischen Titration tritt ein konstanter Fehler auf, wenn die Einwaage 0,3 mg unterschreitet.

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Résumé On décrit un procédé rapide pour le dosage du chlore à l'échelle du milligramme, dans lequel la substance est brulée suivantPregl et le chlore est titré potentiométriquement suivantNorthrop. L'exactitude et la fidélité de la méthode ont été prouvées sur 4 substances étudiées avec 5 dosages pour chacune d'elles. En outre, on a fait des analyses justificatives pour le dosage potentiométrique direct du chlore à l'aide de trois chlorhydrates organiques solubles dans l'eau. Des procédés analogues sont décrits pour le dosage du chlore dans des prises d'essai de l'ordre du dixième de milligramme. Par suite de l'association de la combustion et du titrage potentiométrique, l'erreur reste constante quand la pesée est inférieure à 0,3 mg.

     

Computerized technique in organic microelemental analysis: Part IV: Automated determination of chlorine,bromine, and iodine in organic compounds

The automatic and computerized rapid microanalytical determination of chlorine, bromine, and iodine in organic and organometallic compounds is described. The method consists of combustion of the compound in a large diameter empty tube connected to a titration vessel. The combustion products are transferred from the end of the combustion tube to the titration vessel by means of an automatic reductive SO₂-containing wash. Automatic potentiometric titration with AgClO₄ to the preset endpoint potential, using a combination silver microelectrode, serves as the endpoint detection of the titration of halides. The entire analysis, including automatic preparation of the equipment for the next determination, is programmed in a 6-min cycle. The method is blank-free; the results are accurate. Standard deviations amount to: 0.05, 0.14, and 0.18% absolute for Cl, Br, and I, respectively.The analyzer is interfaced to a real-time, time-sharing computer along with electronic microbalances and other analyzers, as part of the microanalytical laboratory computer service. The results of the analyses are reported on CR-terminals and are stored on magnetic disk for further processing.     

Extension of a temperature-dependent aqueous solvation model to compounds containing nitrogen, fluorine, chlorine, bromine, and sulfur

Most methods for predicting free energies of solvation have been developed or validated exclusively for room temperature. Recently, we developed a model called SM6T for predicting aqueous solvation free energies as a function of temperature for solutes composed of C, H, or O, and here we present solvation model 8 with temperature dependence (SM8T) for predicting the temperature dependence of aqueous free energies of solvation for compounds containing H, C, N, O, F, S, Cl, and Br in the range 273-373 K. We also describe the database of experimental aqueous free energies of solvation used to parametrize the model. SM8T partitions the temperature dependence of the free energy of solvation into two components: the temperature dependence of the bulk electrostatic contribution to the free energy of solvation, which is computed using the generalized Born equation, and the temperature dependence of first-solvation-shell effects, which is modeled by terms proportional to the solvent-exposed surface areas of atoms in functional groups determined entirely by geometry. SM8T predicts the temperature dependence of aqueous free energies of solvation with a mean unsigned error of 0.08 kcal/mol over a database of 4403 measurements on 348 compounds at various temperatures. We also discuss the accuracy of SM8T for predicting the temperature dependence of aqueous free energies of solvation for ions and present free energies of solvation as a function of temperature for two sample ions.     

The microanalysis of fluorine-containing organic compounds. II. the determination of fluorine

Summary The compound is decomposed by fusion with metallic sodium or potassium in a nickel bomb of special design, and the fluorine is titrated with thorium nitrate solution. Several modifications of this titration procedure were first examined as a means of completing the determination, but only one was found suitable, i. e. back-titration of a comparison solution with a standard sodium fluoride solution.When nitrogen and sulphur, which form cyanide and sulphide ions, are present, the procedure has to be modified slightly to overcome their interference.

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Zusammenfassung Organische Fluorverbindungen werden durch Schmelzen mit metallischem Natrium bzw. Kalium in einer Nickelbombe besonderer Konstruktion zerstört und das Fluor mit Thoriumnitratlösung titriert. Einige Modifikationen dieses Titrationsverfahrens wurden zunächst geprüft, aber nur eine davon erwies sich endgültig als für die Bestimmung geeignet: die Rüektitration einer Vergleichalösung mit einer Standardlösung von Natriumfluorid.Bei Gegenwart von Stickstoff und Schwefel bilden sich Cyanidbzw. Sulfidionen, deren störender Einfluß durch eine kleine Abänderung des Verfahrens ausgeschaltet werden muß.

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Résumé Les composés organiques fluorés sont décomposés par fusion avec le sodium métallique ou le potassium dans une bombe de nickel de construction spéciale et le fluor est titré avec le nitrate de thorium en solution. Plusieurs modifications de ce mode de titrage furent d'abord examinées pour terminer le dosage, mais un seul fut trouvé convenable, le titrage par retour d'une solution de comparaison avec une solution de fluorure de sodium.Quand l'azote et le soufre qui forment des ions cyanhydriques et suifhydriques sont présents, le procédé doit être légèrement modifié afin d'empêcher leur interférence.

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The paper byR. Belcher andR. Goulden, Mikrochem.37, 679 (1951) is considered as Part I of this series.     

Computerized technique in organic microelemental analysis III. Automatic determination of fluorine in organic compounds

The automatic and computerized rapid microanalytical determination of fluorine in organic and organometallic compounds is an easily reproducible procedure. The procedure consists of the combustion of the compound in an empty tube; transfer of the combustion products to the titration vessel by automatic wash; and, finally, colorostatic titration of HF with Th(ClO₄), against alizarin red S.The entire analysis and preparation of the equipment for the next determination are programmed in the time of the 6-min cycle.The analyzer is interfaced to the departmental real-time time-sharing computer, along with electronic microbalances and other analyzers, as a part of the microanalytical laboratory computer service.Results of the analyses are reported on CR terminals and are also stored on the magnetic disk for further processing.     

The determination of nitrogen trichloride in liquid chlorine

Methods are described for the determination of nitrogen trichloride over the range of concentrations at which it exists in chlorine manufacture and handling. The methods are based on the conversion of nitrogen trichloride to ammonium chloride by hydrochloric acid and the determination of ammonium by spectrophotometry as the indophenol complex or by potentiometry with an ammonia gas-sensing electrode; higher levels of nitrogen trichloride are determined by titration. For liquid chlorine, a sample is taken in a refrigerated trap containing hydrochloric acid. After that, the chlorine is slowly evaporated at atmospheric pressure. Results of tests are given to prove the reliability of the methods.     

Ultramicrodetermination of nitrogen in organic compounds: Centimilligram determination of nitrogen with sealed tube method

A new improved nitrometer was developed for centimilligram determination of nitrogen by the sealed-tube method. A combustion tube having an internal volume of 1 ml was used and the sample was weighted in a boat made of copper foil, which was made by a simple device. The accurate volume of a gas granule of the blank was evaluated by observation with a micrometer microscope. A standard deviation of 0.240% was rapidly and conveniently obtained with organic compounds having a range of 5.94–66.4% nitrogen.     

Oxygen determination in organic fluorine compounds by means of a glassy-carbon pyrolysis tube

A conventional apparatus for determination of oxygen in organic compounds has been improved for application to organic fluorine compounds. A feature of the apparatus is the use of a pyrolysis tube made of glassy carbon instead of quartz, which eliminates effects due to hydrogen fluoride produced in pyrolysis of the sample. Ten analyses of dexamethasone with the apparatus gave a mean value of 20.44% for oxygen (theory, 20.38%), with a standard deviation of 0.16%. Oxygen in 9 organic fluorine compounds was accurately determined by using the apparatus, with an average error of +0.1%. One analysis by a gravimetric or a coulometric method took about 40 or 25 min, respectively.