Oxidation Kjeldahl

This method was developed to replace the hazardous mercury catalyst required in the original mercuric oxide Kjeldahl method. It has been evaluated through an interlaboratory comparison of catalysts and has been adopted as the official replacement for the mercuric-oxide catalyzed Kjeldahl method. An inter-laboratory evaluation (Berner, 1990) indicated that this method (which uses the copper/titanium catalyst mixture) produces results more closely in agreement with the mercuric oxide catalyst method than methods using a copper sulfate catalyst. As a result of this study, mercuric... 

Oxidative degradation of [B qH q] and [B22H22] C to boric acid is extremely difficult and requires Kjeldahl digestion or neutral permanganate. The heat of reaction obtained from the permanganate degradation leads to a calculated heat of formation for [B qH q] (aq) of 92.5 21.1 kJ/mol (22.1 5.0 kcal/mol) (99). The oxidative coupling of both [B qH q] and has been studied ia some detail (100). 

SCWO Supercritical Water Oxidation TKN Total Kjeldahl Nitrogen TOC Total Organic Carbon TSS Total Suspended Solids WAO Wet Air Oxidation... 

Another approach to the organic nitrogen problem is to use persulfate wet oxidation to convert the nitrogen to nitrate or nitrite, in place of the reduction to ammonia [13,14,24,25]. Results are fully comparable with those from the micro Kjeldahl digestion but the technique is far simpler. The precision should also be higher, since the final step in the measurement, the colorimetric determination of nitrite, is much more precise than any of the ammonia methods. 

Sulfuric acid h2so4 Commercially available concentrated solution is 96% (18 M) H2S04 a dense, syrupy liquid reacts on contact with skin and clothing evolves much heat when mixed with water Organic samples, such as for Kjeldahl analysis (see Chapter 5) also oxides of Al and Ti... 

Total and nitrate nitrogen were determined by Kjeldahl and colorimetric methods, respectively (29,30). Organic matter was determined by the wet oxidation method of Walkley (31). Soil pH was determined with a glass electrode in a 2 1 mixture of water and soil. 

Nitrogen (i) by Kjeldahl digest (ii) elemental analyser, or (iii) dichromate oxidation. 

Kjeldahl s method17, which consists of oxidation by a mixture of sulphuric acid and... 

The choice between oxidation by the Kjeldahl or the Schoniger technique is not clear-cut. Both methods will usually yield quantitative reactions, both will occasionally give incomplete combustion and low results, depending on the family of substances analysed and on the slight modifications introduced into the procedures in different laboratories. 

The nitric oxide was determined as usual—by absorption in water and titration. Control experiments on the combustion of the gas at low temperature and of analysis according to Kjeldahl (reduction of nitric and nitrous acids to NH3 by the action of MgAl-alloy in alkaline solution, distillation and absorption of NH3 by acid) convinced us that the gas contained no noticeable traces of sulphur and that the acidity as ordinarily determined depends on nitric and nitrous acids. 

The method was checked by analysis according to Kjeldahl (reduction of the fixed nitrogen to ammonia) and by analysis of measured amounts of nitric oxide let into the cylinder from a pipette. 

M. Berthelot. found that many nitrogenous organic compounds furnish ammonia when heated with hydriodic acid and J. Kjeldahl showed that the nitrogen of many nitrogenous compounds is all converted into ammonia or ammonium sulphate when heated with cone, sulphuric acid—in the case of nitro-eompounds and cyanides the reaction is not always quantitative. The reaction proceeds more satisfactorily in the presence of mercury or mercuric oxide, copper, potassium hydrosulphate, sugar, phenol, benzoic acid, and analogous compounds. This reaction has been discussed by C. Arnold, A. Atterberg, C. Budde and C. V. Sehon,... 

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