Acetic Acid polarography

Polarography has also been applied to the determination of potassium in seawater [535]. The sample (1 ml) is heated to 70 °C and treated with 0.1 M sodium tetraphenylborate (1 ml). The precipitated potassium tetraphenylborate is filtered off, washed with 1% acetic acid, and dissolved in 5 ml acetone. This solution is treated with 3 ml 0.1 M thallium nitrate and 1.25 ml 2M sodium hydroxide, and the precipitate of thallium tetraphenylborate is filtered off. The filtrate is made up to 25 ml, and after de-aeration with nitrogen, unconsumed thallium is determined polarographically. There is no interference from 60 mg sodium, 0.2 mg calcium or magnesium, 20 pg barium, or 2.5 pg strontium. Standard eviations at concentrations of 375, 750, and 1125 pg potassium per ml were 26.4, 26.9, and 30.5, respectively. Results agreed with those obtained by flame photometry. 

The electrochemical reduction of aryllead triacetates was smdied by Chobert and Devaud82, as a re-examination of some previous work83 to detect the role of intermediates such as [ArPb(OAc)2]V The reductions were carried out by polarography in acetic acid or acidic alcohol solutions and show three diffusion controlled waves. The first step involves a single electron transfer to produce a radical anion which dimerizes, arylates the electrode or hydrolyzes to phenol ... 

Song et al. [11] developed a polarographic method for the determination of mefenamic acid in tablets, which was based on rapid nitrosation of mefenamic acid with sodium nitrite in acetic acid, and subsequent measurement of the A-nitroso derivative of mefenamic acid by linear-sweep polarography. The method is simple, sensitive, and specific, and was characterized by a detection limit of 2 x 10 7 mol/L. 

Sodium nonatungstosilicate is a white solid, which is slightly soluble in water. The solution is metastable at all pH values, but it changes slowly. The best characterization is polarography in 1 M sodium acetate-1 M acetic acid buffer The polarogram shows only one four-electron wave with 1/2 = — 0.80 V versus SCE. The polyanion can be characterized in the solid state by its IR spectrum (KBr pellet, cm ) 985, 940(sh), 930, 865, 848(sh), 808, 712, 552, 530, 490(sh), 435, 373, and 335. 

Sodium /3,-undecatungstosilicate is a white water-soluble solid which, in solution, slowly changes into the P2 isomer (Compound F). It is characterized by polarography in 1 M sodium acetate-1 M acetic acid The polarogram shows two two-electron waves at - 0.63 and - 0.83 V versus SCE. 

The potassium /33-undecatungstosilicate is a white solid, which is soluble in water. In solution it slowly converts into the a isomer. It can be characterized by polarography in M sodium acetate-IM acetic acid buffer The... 

The acid and its potassium salt are white solids, which are soluble in water. The polyanion is stable below pH 4.5. It is characterized by polarography of the fresh solution in M sodium acetate-IM acetic acid buffer The polarogram shows two one-electron and one two-electron waves at — 0.24, — 0.48, and — 0.95 V versus SCE, respectively. The UV spectrum in aqueous solution shows e" 2 58 = 47, 000, and e "232 = 19, 200. 

The various oxidation states of sulfur have been determined by polarography applying such techniques to sample types including drinks, wastewaters, petroleum, and environmental samples (anoxic lake waters, sediments/sediment pore waters). Species detected have included S , SO, S20. in NaOEI solution yields a peak potential arovmd — 0.75 V versus SCE. Additions to the solution of acetic acid with subsequent purging will remove EI2S, enabling the detection of S203 and SOf at respective potentials at — 0.15 and — 0.63 V versus SCE. 

The methanol azeotropic-distillation procedure was also applied to a synthetic solution of acrylonitrile in 6% hydrochloric acid extractant. Polarographic analysis of the methanol-acrylonitrile azeotrope was not possible, however, owing to the presence of an appreciable amount of free acid originating from the hydrochloric acid extractant, in the distillates, which interfered in the polarography of acrylonitrile. In a further experiment, a 6% hydrochloric acid solution of 47.3 ppm of acrylonitrile was neutralised by the addition of a small excess of solid calcium oxide. Methanol and sulfuric acid were added and the azeotropic distillation continued as before. It can be seen from Table 11.1 (sample B) that under these conditions more than 90% of the added amount of acrylonitrile was recovered in the first 8 ml of methanol distillate. A preliminary neutralisation with lime was incorporated, therefore, into the procedure for determining acrylonitrile in 6% hydrochloric acid extraction liquids. This procedure should also be applicable to the determination of acrylonitrile in the 3% aqueous acetic acid extractant recommended by the Food and Drug Administration (FDA) [3]. 

Product analysis was carried out using a variety of techniques including polarography, gas chromatography, and Kjeldahl analysis. No dimerized products were detected by gas chromatography. These mechanisms differ from the dimerization process typical of the radical reactions associated with the Kolbe mechanism for such species as acetic acid. ... 

The use of differential pulse polarography to determine neomycin sulphate in aqueous solutions has been described by Siegerman et all2. Following acid hydrolysis of neomycin, the solution was adjusted to pH 4 and 0.1M acetate... 

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