Indirect polarographic microdetermination of chlorine or bromine in organic compounds

A polarographic method for the microdetermination of chlorine or bromine in organic compounds is based on oxygen-flask combustion followed by an exchange reaction of chloride or bromide with excess of solid silver chromate, and polarographic determination of the chromate liberated. The method has been applied satisfactorily to a wide range of chlorine or bromine organic compounds with a coefficient of variation not exceeding 1%.     

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.

     

Iodometric microdetermination of sulphur in organic compounds by an amplification reaction

A new method is described for the iodometric microdetermination of sulphur in organic compounds, using a 12-fold amplification reaction after oxygen-flask combustion. The method is based on reaction of the resulting sulphuric add with an excess of saturated barium bromate solution. The unreacted barium bromate is precipitated by addition of acetone, filtered off, redissolved in hot water and after addition of an excess of iodide and acid, the iodine liberated is titrated with thiosulphate. The method is simple, rapid, highly accurate, and of wide application in the microanalysis of organosulphur compounds containing other common acid-forming elements.     

Turbidimetric determination of some sulphur compounds in ethanol from fermentation

A simple method is described which can be used for the determination of certain sulphur compounds found in industrial ethanol obtained from fermentation of molasses. The method is based on the turbidimetric determination of sulphate after the sample has been treated with dilute hydrogen peroxide solution, by precipitation of the sulphate with barium chloride under appropriate conditions. Several samples of fermentation ethanol have been analysed by this method and the sulphur contents found compared with the total acidity.     

Simultaneous microdetermination of carbon,hydrogen, mercury,chlorine, bromine and sulphur in organic compounds

A simple, reliable method for the simultaneous microdetermination of carbon, hydrogen, mercury, chlorine (or bromine) and sulphur in organic compounds is described. The intermediate storage technique is used. Sulphur and the halogens are absorbed on electrolytic silver and determined gravimetrically or titrimetrically. Mercury is absorbed on gold wire, and is weighed as the metal or desorbed and determined by a mercury-8-hydroxy-quinoline method.     

The microdetermination of C-methyl groups in organic compounds

Summary Existing standard procedures for the microdetermination of C-methyl groups in organic compounds have been discussed, and a modified micromethod, in which the oxidation of the sample and the distillation of the resulting acetic acid are carried out simultaneously, has been presented. New and useful information on the stability of acetic acid, when heated in presence of chromic-sulphuric acid mixture of varying strengths, for periods ranging between 15–90 minutes, and at temperatures varying between 130–300° C, has been given. A number of simple organic substances have been analysed for their C-methyl values by the different procedures, and the results have been recorded and discussed.

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Zusammenfassung Bekannte Verfahren für die Mikrobestimmung von C-Methylgruppen in organischen Verbindungen wurden diskutiert und eine modifizierte Mikromethode vorgeschlagen, bei der die Oxydation der Substanz und die Destillation der dabei entstehenden Essigsäure gleichzeitig durchgeführt werden. Neue und wertvolle Angaben über die Beständigkeit der Essigsäure gegenüber heißer Chromsäure-Schwefelsäure verschiedener Konzentration bei Einwirkungszeiten von 15 bis 90 Minuten und Temperaturen zwischen 130 und 300° werden gemacht. Eine Reihe einfacher organischer Substanzen wurden nach verschiedenen Verfahren auf ihren C-Methylgehalt untersucht: die Ergebnisse werden angeführt und diskutiert.

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Résumé On a discuté les procédés «standards» existant pour doser les groupes C-méthylés dans les composés organiques et l'on a présenté une microméthode modifiée dans laquelle l'on effectue simultanément l'oxydation de l'échantillon et la distillation de l'acide acétique résultant. On a donné une indication nouvelle et utile sur la stabilité de l'acide acétique chauffé en présence du mélange sulfochromique de forces différentes, pendant des durées allant de 15 à 90 minutes et à des températures comprises entre 130 et 300° C. On a analysé un certain nombre de substances organiques du point de vue de leurs teneurs en C-méthylés au moyen de différents procédés et l'on a rassemblé et discuté les résultats.

     

Photometric microdetermination of acetyl groups in organic compounds

A method for the microdetermination of acetyl groups is described which combines features of the known transesterification and the hydroxamate methods. All acetyl groups attached to oxygen or nitrogen are converted to methyl acetate which is distilled off and determined photometrically as the iron complex of the acethydroxamic acid. A slightly modified technique permits the selective determination of acetyl groups in the presence of formyl groups.     

A polarographic study of some N-containing organic compounds under aquarium conditions

Summary Differential pulse polarography has been used to monitor organic compounds containing various oxidation states of nitrogen in aquarium situations at the trace level. The absorption of two classes of compounds (diazo dyes and aromatic nitro compounds) has been followed in plants and daphnae and it is concluded that if these compounds metabolise to electroactive species they must be stored in the body of the aquarium constituents and are not excreted back into solution.The main body of this paper was presented at a conference in St. Andrews (19th–20th June 1975) entitled The Application of New Techniques in Environmental Analysis, organised by the Scothish Region of the Analytical Division of the Chemical Society.     

Coulometric microdetermination of carbon and hydrogen in organic compounds

Summary An apparatus for accurate determination of carbon and hydrogen has been developed, based on a previously described coulometric Karl Fischer method for determination of small amounts of water in solids. Hydrogen and carbon in a sample are oxidized to water and carbon dioxide, respectively. The water is trapped first, and the carbon dioxide is converted into water by lithium hydroxide and determined in a coulometric cell. Then the water from the hydrogen is released and determined in the same cell. An alternative method for the determination of hydrogen alone with very high precision has also been developed. Samples weighing 0.1–5 mg can be analysed and the standard deviations obtained for a complete C, H determination are ±0.17% and ±0.08%, respectively. That for determination of hydrogen alone is ±0.009%.

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Zusammenfassung Eine Apparatur zur exakten Bestimmung von Kohlenstoff und Wasserstoff wurde auf der Basis einer früher beschriebenen coulometrischen Karl-Fischer-Methode zur Bestimmung geringer Wassermengen in Feststoffen entwickelt. Wasserstoff und Kohlenstoff werden zu Wasser bzw. Kohlendioxid oxydiert. ZunÄchst wird das Wasser absorbiert und das Kohlendioxid anschlie\end mit Lithiumhydroxid in Wasser übergeführt und in einer coulometrischen Zelle bestimmt. Das vom Wasserstoff herrührende Wasser wird in derselben Zelle bestimmt. Eine alternative, sehr genaue Bestimmungs-methode nur für Wasserstoff wurde ebenfalls entwickelt. Bei Probenmengen von 0,1–5 mg betrÄgt bei einer vollstÄndigen CH-Bestimmung die Standardabweichung ±0,17% bzw. ±0,08%; für die alleinige Wasserstoff-Bestimmung ist die Standardabweichung ±0,009%.

     

Simultaneous microdetermination of iodine and sulfur in organic compounds

A simple and rapid method for the simultaneous microdetermination of iodine and sulfur in organic compounds is described. The procedure utilizes the Schöniger flask method for the combustion, the iodide ions titration with 0.01 N mercuric perchlorate solution and diphenylcarbazone as indicator and the sulfate ions titration with 0.01 M barium perchlorate solution and dimethylsulfonazo III as indicator. The results obtained are in good agreement with calculated values.     

Simultaneous microdetermination of sulfur and phosphorus in organic compounds

A simple method for the simultaneous determination of sulfur and phosphorus in 3–8 mg organic sample is presented. Following oxidative combustion by the oxygen flask method, sulfate is precipitated by addition of a known amount of Ba(II) and the excess of the latter is measured polarographically. After filtration, the quinoline phosphomolybdate method is used to precipitate phosphate; the unreacted Mo(VI) is determined polarographically. The mean relative error for 13 determinations was 2.99% for S and 4.07% for P; the mean relative standard deviation was 1.43 and 4.19%, respectively.     

Automated determination of sulphur in organic compounds

The paper reviews methods of sulphur determination over the last 120 years. Classical methods are presented in a historical view, and the present state of automatic procedures of sulphur estimation is discussed. 104 key references concerning sulphur analysis are cited. On the basis of the present level of the development of elemental analysis, a prognosis of directions of the development of sulphur microanalysis is attempted.     

有机化合物中硫元素微量测定方法的一些改良

作为有机元素微量定量分析方法系列报道之一,本文对目前普遍应用的氧瓶燃烧分解样品,钡盐法滴定有机硫的分析方法进行了规范化,探讨了溶液pH对测定的影响,检测了磷元素及氟元素对测定的干扰,并建立了适用于测定含磷有机化合物中硫元素的钡盐滴定法.针对钡盐法测定低含量硫元素时误差较大,本文建立了基于氯冉酸钡与硫酸根离子反应的分光光度法,该法准确可行,适用于测定低含量有机硫元素.