Titrimetric methods for the micro determination of sulphur and halogens in organic compounds by the rapid combustion procedure : The simultaneous determination of sulphur and the halogens

The quantitative absorption of the gaseous products arising from the oxidative degradation of organic materials containing sulphur, halogens, (chlorine, bromine and iodine) oxygen and nitrogen, by the rapid empty tube combustion has been studied further. Satisfactory titrimetric methods for the simultaneous determination of sulphur and any one or two of the halogens in the presence or absence of nitrogen have been developed.     

Polarographic microdetermination of halogens in organic compounds after oxygen flask combustion

A method for the microdetermination of organic compounds containing halogens, by a polarographic finish, is reported. After the combustion of the organic sample in the oxygen flask, the products are absorbed in a suitable absorbent and chemically treated to produce Cl(-), Br(-), BrO(3)(-) or IO(3)(-) ions in solution before the polarography. The method is applicable to partially, highly, and fully halogenated aromatic and aliphatic compounds, whether solid or liquid. The results are generally within the acceptable limits of error.     

The microdetermination of nitrogen in organic compounds by the rapid combustion process

Summary A method is described for the microdetermination of nitrogen in organic compounds which is based on the rapid combustion process. The sample is burned in a fast stream of carbon dioxide-oxygen mixture in a tube provided with an empty combustion chamber. The products formed are led over hot copper, thus removing excess of oxygen and reducing the nitrogen oxides. The nitrogen is swept out with the transport gas into a nitrometer, collected over potash solution and measured. A single determination may be completed in about 20 minutes, which includes the cooling period of the nitrogen prior to measuring the volume. Compounds which burn only with difficulty when subjected to thePregl-Dumas procedure have been analysed satisfactorily by the new method.It is shown that commercial oxygen contains up to 0.07% of inert gases and is therefore unsuitable in the nitrogen method for oxidising nitrogenous chars. An electrolytic cell which provides a continuous supply of blank-free oxygen, and hydrogen for regeneration of the copper filling has been constructed as a permanent part of the apparatus.Complete reduction of the nitrogen oxides and oxygen by the large amount of metallic copper (ca. 20 cm) is accomplished at the flow rate range of 15–20 ml per minute employed.Evidence has been obtained that present-day quartz tubing of British manufacture becomes porous in the course of time when heated in contact with copper oxide on copper in an inert atmosphere of carbon dioxide, giving high blanks.

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Zusammenfassung Ein Schnellverfahren zur Mikrobestimmung von Stickstoff in organischen Verbindungen wird beschrieben. Die Probe wird in einem raschen Kohlen-dioxyd-Sauerstoff-Strom in einem Rohr mit besonderem T-förmigem Verbrennungsteil vergast. Die Verbrennungsprodukte leitet man über erhitztes Kupfer, um überschüssigen Sauerstoff zu entfernen und die Oxyde des Stickstoffes zu reduzieren. Der Stickstoff wird mit Hilfe des Transportgases in ein Azotometer ausgespült, über Kalilauge aufgefangen und gemessen. Eine Einzelbestimmung dauert etwa 20 Minuten einschließlich der für die Abkühlung des Azotometers nötigen Zeit. Substanzen, die nachPreglDumas nur schwer analysierbar sind, konnten nach der neuen Methode befriedigend untersucht werden.Handelsüblicher Sauerstoff enthält bis zu 0,07% inerte Gase und eignet sich daher nicht zur Verbrennung stickstoffhaltiger Verkohlungsprodukte. Ein Gerät zur kontinuierlichen elektrolytischen Gewinnung blindwertfreien Sauerstoffes, das außerdem auch Wasserstoff zur Reduktion der Kupferdrahtfüllung liefert, bildet einen Teil der angegebenen Apparatur.Die vollständige Reduktion der Stickstoffoxyde und des Sauerstoffes ist bei der Strömungsgeschwindigkeit von 15 bis 20 ml/Minute durch die große Menge metallischen Kupfers sichergestellt.Es hat sich gezeigt, daß derzeit Quarzrohre britischer Herkunft im Lauf der Zeit beim Erhitzen in Kohlendioxydatmosphäre in Gegenwart von Kupfer oder Kupferoxyd porös werden und daher hohe Blindwerte verursachen.

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Résumé On décrit une méthode pour le microdosage de l'azote dans des composés organiques, basée sur le procédé de combustion instantanée. L'échantillon est brûlé dans un rapide courant de mélange CO₂-O₂ dans un tube muni d'une chambre à combustion vide. Les produits formés sont dirigés sur du cuivre chauffé ce qui fixe l'oxygène en excès et réduit les oxydes d'azote. L'azote est balayé vers le nitromètre, recueilli sur la solution de potasse et mesuré. Une seule détermination peut se faire en 20 minutes environ y compris la période de refroidissement de l'azote avant mesure du volume. Les composés ne brûlant qu'avec difficulté quand on les traite par la méthode deDumas-Pregl ont été analysés d'une manière satisfaisante quand on les traite par le nouveau procédé.On montre que l'oxygène commercial contient jusqu'à 0,07% de gaz inertes et que par conséquent, il ne convient pas dans la méthode à l'azote pour oxyder les goudrons azotés. Une cuve à électrolyse qui fournit un débit continu d'oxygène exempt d'impuretés et de l'hydrogène pour la régénération de la tournure de cuivre a été installée comme faisant partie intégrante de l'appareil.La réduction complète des oxydes de l'azote et de l'oxygène par le grand excès de cuivre métallique (environ 20 cm) s'effectue à la vitesse de 15 à 20 ml par minute de fonctionnement. On a mis en évidence le fait que les tubes de quartz actuellement fabriqués par les usines anglaises deviennent poreux au cours du temps quand on les chauffe dans une atmosphère inerte de gaz carbonique, ce qui donne lieu à des témoins élevés.

     

Simultaneous microdetermination of carbon, hydrogen and chlorine or bromine in organic compounds by various rapid empty-tube combustion methods

A standard Pregl absorption tube packed with polyurethane foam mixed with a cation-exchanger in the silver form, backed with a layer of “Anhydrone”, and connected between the water and carbon dioxide absorption tubes and kept at room temperature, has been employed successfully for the simultaneous determination of chlorine or bromine together with carbon and hydrogen. This foam tube is suitable for use with the Belcher-Ingram, rapid straight empty-tube and rapid flash-combustion methods.     

A rapid method for the microdetermination of nitrogen in organic compounds using a flushed-oxygen combustion tube

A micromethod to determine nitrogen in organic compounds of 1–1.5 mg has been studied by the combustion method where oxygen is flushed into an empty combustion tube heated at 850 °C. The flushing nozzle is consisted of two silica filters in a L-tube and oxygen flowing out of the nozzle rapidly oxidizes the organic vapor gasified in a sample heater. Excess oxygen and nitrogen oxides are absorbed and reduced with reduced copper heated at 500–600 °C.     

Titrimetric microdetermination of certain sulphur-containing organic compounds by oxidation with alkaline potassium permanganate

A titrimetric procedure is described for the microdetermination of some mercaptans and sulphur-containing amino-acids by oxidation with alkaline potassium permanganate at room temperature in presence of barium ions. The procedure can be applied to 0.002-0.025M solutions with an average deviation of 0.1-0.5%. The effect of variation in the amount of alkali and barium chloride and in the reaction period, on the stoichiometry of the oxidation reactions, has also been studied.     

A rapid combustion technique for the determination of small amounts of sulphur and halogens in organic liquids

A rapid combustion technique for the determination of small amounts of sulphur and halogens in organic liquids is described. The technique, in the first instance, refers to the Shell-Braun quartz tube combustion unit and offers an appreciable extension of the working area of this apparatus.     

Rapid micro combustion methods for the determination of elements in organic compounds

Summary Advantages of the rapid combustion process for the micro determination of carbon and hydrogen, sulphur, and halogen are discussed, and methods for their estimation are described which have been adopted for routine analysis.

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Zusammenfassung Die Vorteile eines raschen Verbrennungsvorganges für die Mikrobestimmung von Kohlenstoff, Wasserstoff, Schwefel und Halogen werden beschrieben. Methoden für deren quantitative Bestimmung, die sich besonders für Serienanalysen bewährt haben, werden mitgeteilt.

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Résumé On discute les avantages du procédé rapide de combustion pour le microdosage du carbone, de l'hydrogène, du soufre et des halogènes et l'on décrit les méthodes pour leur dosage qui ont été adaptées dans les analyses en série.

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With 5 Figures.     

Spectrophotometric microdetermination of bismuth in organic compounds after oxygen-flask combustion

A method has been developed for the micro and submicro determination of bismuth in organic compounds, based on combustion in an oxygen-filled flask, provided with a silica spiral instead of the conventional platinum holder (which alloys with bismuth). After absorption of the products in hydrochloric acid (1 + 1), the solution is chemically treated to convert the bismuth into the orange-yellow BiI(-)(4) complex, then the absorbance is measured at 465 nm. Analysis of 12 organic compounds containing 28-74% of bismuth yielded satisfactory results with a maximum standard deviation of 0.4%.     

New iodometric methods for the microdetermination of arsenic in organic compounds

New methods are described for the iodometric microdetermination of arsenic in organic compounds after wet digestion or oxygen flask combustion. After evaporation of the arsenic solution to dryness and dissolution of the residue in water, acetone is added and the solution is treated with iodide-iodate and the iodine liberated (by the interfering acids and the first dissociation step of arsenic acid) is reduced with thiosulphate. The KH(2)AsO(4) left is then reacted with zinc sulphate in presence of excess of KI and KIO(3). Acetone is added and the liberated iodine is titrated with thiosulphate. This titration corresponds to the second and third dissociation steps of arsenic acid and is used to calculate the arsenic content of the compound. When arsenicals not containing sulphur are decomposed by the oxygen flask method, the arsenic acid solution obtained is reacted directly with zinc sulphate in presence of KI and KIO(3) and the iodine released is titrated with thiosulphate. In this case, the titration corresponds to all three dissociation steps of arsenic acid. The average recoveries obtained by the two methods are 99.5 and 99.9%, respectively.     

Titrimetric microdetermination of inorganic or organic mercury by amplification reactions

A simple titrimetric method for estimation of 0.05-7 mg of Hg(II) is presented. The acidic sample solution is treated with a measured and excessive amount of iodide, then mercuric iodide is extracted at ph 2-3.5, and the unreacted iodide is determined iodometrically after 6- or 36-fold amplification by use of bromine water for oxidation of iodide to iodate. Periodate oxidation of excess of iodide gives 24-fold amplification. The coefficient of variation does not usually exceed 1% for above 1 mg of mercury but increases to 4% at the 0.05-mg level. The 6-fold amplification method is used for microdetermination of organically bound mercury following oxygen-flask combustion. The average absolute error for 10 determinations (3 compounds) amounted to +/-0.6%; one determination takes less than one hour.     

Polarographic microdetermination of sulphur in organic compounds after oxygen flask combustion

Summary Three polarographic micro-methods are described for the determination of sulphur in organic compounds after oxygen-flask combustion. The products are converted into sulphuric acid by oxidation with hydrogen peroxide, the excess of which is expelled through boiling. The methods are based upon allowing the sulphuric acid to react with an excess of barium iodate or bromate, then recording polarographically the cathodic reduction wave of the iodate or bromate ion. The bromate methods are superior to the iodate method being simpler and more rapid, and the results are correct to within ca. ±0.5%.

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Zusammenfassung Drei polarographische Mikromethoden zur Bestimmung von Schwefel in organischen Verbindungen nach deren Verbrennung im Sauerstoffkolben wurden beschrieben. Die Verbrennungsprodukte werden durch Oxydation mit Wasserstoffperoxid in Schwefelsäure umgesetzt. Der Überschuß des Oxydationsmittels wird durch Kochen zerstört. Die Schwefelsäure läßt man mit überschüssigem Bariumjodat oder -bromat reagieren und mißt dann polarographisch die kathodische Reduktionswelle des Jodats oder Bromats. Die Bromatmethode ist der Jodatmethode überlegen, da sie einfacher und rascher zu Resultaten führt, die innerhalb ±0,5% korrekt sind.

     

Potentiometric microdetermination of cadmium in organic compounds after oxygen flask combustion

The sample is burnt in an oxygen flask and the combustion products are absorbed in lM HNO₃. After removal of interfering gases by boiling, the solution is transferred to the titration cell and neutralized with NaOH in the presence of methyl red; Cd(II) is finally titrated potentiometrically in a buffered 50% ethanolic medium with 0.01M sodium diethyldithiocarbamate in 50% ethanol. A silver/sulphide ion-selective electrode and a double junction reference electrode containing a 10% KNO₃ solution in 26% ethanol in the outer compartment are used in combination with a Titroprocessor to detect the end point. The results obtained are very accurate and reproducible: the maximum error does not exceed 0.09%, the recovery of cadmium is in the range 99.67 to 99.95% and the rel. standard deviation is 0.05%. The potentiometric titration with diethyldithiocarbamate, which is useful to determine small Cd(II) amounts down to 30g (2g ml^–1), as well as the oxygen flask combustion of organic cadmium compounds are discussed.     

Titrimetric determination of some organic compounds with bromine chloride

Bromine chloride is used in hydrochloric acid medium as a standard reagent for the rapid and precise determination of organic compounds by direct or indirect titrimetric methods. Hydrazine and its aryl derivative undergo a 4-electron change. Carbonyl compounds are determined by reaction with excess of 2,4-dinitrophenylhydrazine and estimation of the surplus. Sulphanilamide undergoes a substitution reaction in 1:3 molar ratio to bromine chloride. Thiobarbituric acid and thiourea or its alkyl derivatives show an 8-electron change but aryl thioureas also undergo nuclear bromination. Thiosemicarbazide and semicarbazide give a 10- and a 2-electron change respectively. In the direct titration, methionine is oxidized to its sulphoxide whereas cystine and cysteine form cysteic acid. In presence of bromide, glutathione forms the sulphonic acid but in the presence of iodide the product is the disulphide. The analytical results obtained by bromine chloride method are compared favourably with those afforded by established procedures.     

Titrimetric determination of maleinimide and acrylate groups in organic compounds

A simple procedure is proposed for determining the concentration of maleimide and acrylate groups in organic compounds based on the addition of morpholine to the activated double bond by the Michael reaction, followed by the potentiometric titration of the reaction mixture with 1 M HCl in ethanol. The applicability of the method to N-substituted maleimides with aromatic, aliphatic, and oligomeric substituents, as well as to acrylates and acrylonitrile, is verified. It is demonstrated that maleimides and acrylates can be determined simultaneously.     

Ultramicro determination of organic halogens using sealed tube dry combustion method

A sealed tube dry combustion method that is simple, accurate, and precise for ultramicro determination of halogens in organic compounds has been developed. Samples below 1 mg are heated at 580 °C for 1 h in an electric furnace. After the combustion and absorption of the gaseous halogen, the interior of the tube is rinsed. Subsequent titration is carried out potentiometrically with silver nitrate and yielded standard deviations of 0.21% for chlorine, 0.17% for bromine, and 0.25% for iodine.     

Microdetermination of halogens in organic compounds

Summary Safford andStragand have described a method for the microdetermination of halogens using a silver-gauze-absorbent. The procedure is very simple, but unfortunately the results are not precise enough to enable the method to be recommended.The method has been modified. The sample is burned in an atmosphere of oxygen using a platinum catalyst, and the halogen formed is quantitatively absorbed on electrolytic silver wool in a special absorption-funnel, which is then weighed. The method is precise and accurate (standard deviation of the results: 0.12 per cent). Silver wool presents a much greater surface than silver-gauze and absorbs on an average 160 mg of chlorine per gram, i. e. forty or fifty times as much as a piece of silvergauze of the same dimensions. The charge in an absorption-funnel therefore has a long life for routine analysis of halogen compounds. The operating temperature range of the silver-wool is wide, so that precise control is not neccessary. The method compares favourably in accuracy, precision and simplicity with established methods.

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Zusammenfassung Safford undStragand veröffentlichten eine Methode zur Mikro-Halogenbestimmung mit Hilfe eines Silberdrahtnetzes als Absorptionsmittel. Dieses Verfahren ist sehr einfach, aber seine Resultate leider nicht genau genug, um es zu empfehlen. Die Methode wurde daher modifiziert. Die Substanz wird in einer Sauerstoff-Atmosphäre über einem Platinkontakt verbrannt, das Halogen quantitativ in einem besonderen Absorptionsröhrchen über elektrolytischer Silberwolle absorbiert und dann gewogen. Diese Methode ist genau und verläßlich (mittlere Abweichung der Resultate: 0,12%). Silberwolle bietet eine viel größere Oberfläche als Silberdrahtgeflecht und absorbiert durchschnittlich 160 mg Chlor pro Gramm, das heißt 40- bis 50mal mehr als Silberdrahtgeflecht gleichen Ausmaßes. Die Füllung eines Absorptionsr öhrchens reicht daher für viele Serienanalysen von Halogenverbindungen. Das geeignete Temperaturbereich für Silberwolle ist groß, eine genaue Kontrolle daher nicht nötig. Die Genauigkeit und Einfachheit der Methode ist auch im Vergleich mit bekannten Analysenverfahren durchaus zufriedenstellend.

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Résumé Safford etStragand ont décrit une méthode de microdosage des halogènes par fixation sur toile d'argent. La technique en est très simple mais elle ne permet pas d'obtenir des résultats de précision suffisante. Elle a été modifiée par les auteurs.La prise d'essai est brûlée en atmosphère d'oxygène en présence d'un catalyseur de platine et les halogènes formés sont quantitativement fixés sur de la laine d'argent électrolytique dans un tube d'absorption spécial qui est ensuite pesé. La méthode est précise et exacte (l'écart type des résultats est égal à 0,12 pour cent). La laine d'argent présente une surface beaucoup plus élevée que la toile d'argent et fixe en moyenne environ 160 mg de chlore par gramme, soit, pour le même encombrement, quarante à cinquante fois plus que la toile d'argent. Il en résulte une longue durée de la charge du tube d'absorption lors d'analyses en série des composés halogénés. La température de la laine d'argent peut varier dans un large domaine de sorte qu'il n'est pas nécessaire d'en assurer une régulation précise. La méthode se compare favorablement aux méthodes classiques quant à son exactitude, sa précision et sa simplicité.

     

Titrimetric microdetermination of sulfur in compounds containing alkali or alkaline earth

Summary The titrimetric dry combustion method can be employed for micro-determination of sulfur in organic compounds containing both alkali metal or alkaline earth metal and sulfur.The residue of alkali or alkaline earth sulfate in the boat, formed during the combustion, is fused with 3 to 4 times its weight of boron trioxide, whereby sulfur trioxide is displaced by the boron trioxide.

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Zusammenfassung Die Bestimmung des Schwefels durch Verbrennung und Titration der gebildeten Schwefelsäure kann mit organischen Verbindungen ausgeführt werden, die Alkalien oder alkalische Erden enthalten.Der Metallsulfate enthaltende Verbrennungsrückstand wird im Schiffchen mit der 3- bis 4fachen Menge Bortrioxyd versetzt. Beim darauffolgenden Erhitzen wird das Schwefeltrioxyd in Freiheit gesetzt.

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Résumé On peut employer la méthode par combustion à sec et titrage pour le dosage du soufre dans des composés organiques contenant un métal alcalin ou un métal alcalino-terreux.Le résidu de sulfate alcalin ou alcalino -terreux formés pendant la combustion dans la nacelle est fondu avec trois ou quatre fois son poids de trioxyde de bore; l'anhydride sulfurique est déplacé par le trioxyde de bore.