(Determination of Nitrogen in Shale Oil and Petroleum)Effects of Digestion Temperature on Kjeldahl Analyses

Lake, Goose; McCutchan, Philip; Meter, Robin Van; Néel, Jean

doi:10.1021/ac60059a028

Cited by 51 publications

(15 citation statements)

References 6 publications

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“…The advantage of increasing the amount of potassium sulfate used, other than shortening of the digestion time, is that in many cases theoretical results are obtained which are not possible with the use of the conventional 10 grams of potassium sulfate. This has been confirmed by various workers (8,32,47).…”

Section: Digestionsupporting

confidence: 81%

Kjeldahl Method for Organic Nitrogen

Bradstreet¹

1954

Anal. Chem.

493

300

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THE extent to which the Kjeldahl method has been applied to organic analysis has led to the publication of many data. From time to time, reviews (14,16, 66) have been published covering both macro-and micromethods. Comprehensive reports on microchemical methods have been made by Willits and Ogg (71, 72). In a previous paper (9), the method was reviewed from its inception to 1939. This report covers the period from 1939 to

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Section: Digestionsupporting

confidence: 81%

Kjeldahl Method for Organic Nitrogen

Bradstreet¹

1954

Anal. Chem.

493

300

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“…Add a sample of the proper size from a weighing pipet if a volatile liquid, or by weighing in a small porcelain crucible-e.g., Coors 00000 size-if a solid or nonvolatile liquid. (While a 1-gram sample is desirable because of ease of digestion temperature control, it may vary from 0.1 to 3 grams according to expected magnitude of nitrogen content, 3). After addition of the sample, wash down the neck of the flask with an additional 20-ml.…”

Section: Methodsmentioning

confidence: 99%

Determination of Nitrogen

McCutchan¹,

Roth²

1952

Anal. Chem.

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“…However, the values obtained by different workers cannot be strictly compared because the barometric pressure during temperature measurements is not always stated. Comparison of Tables 15 and 16 indicates that nitrogen is not lost during Kjeldahl digestion until the temperature exceeds about 400° C. Lake et al (1951) found that serious loss of nitrogen occurred during Kjeldahl digestion of tar bases and ammonium oxalate when the temperature of digestion was above 420° C. and concluded that the upper safe temperature in digestion is about 410° C.…”

Section: Loss Of Sulphuric Acid During Kjeldahl Digestionmentioning

confidence: 99%

“…Interest has been focused mainly on the effects of different catalysts and oxidizing agents, and most workers have apparently failed to realize the extent to which the temperature of digestion J. M. BREMNEB affects the rate and completeness of digestion. However, clear evidence of the importance of temperature has emerged from recent work by Ogg & Willits (1950), Lake, McCutchan, Van Meter & Neel (1951), Perrin (1953), andMcKenzie &Wallace (1954), who showed that even refractory compounds such as nicotinic acid and pyridine can be decomposed rapidly and completely to ammonium by digesting with sulphuric acid containing a high concentration of potassium sulphate using mercury as catalyst. Further evidence of the importance of temperature in Kjeldahl digestion is provided by Tables 6, 10, 11, 13 and 14.…”

Section: Loss Of Sulphuric Acid During Kjeldahl Digestionmentioning

confidence: 99%

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Determination of nitrogen in soil by the Kjeldahl method

1960

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1. The reliability of the Kjeldahl method for the determination of nitrogen in soils has been investigated using a range of soils containing from 0·03 to 2·7% nitrogen.2. The same result was obtained when soil was analysed by a variety of Kjeldahl procedures which included methods known to recover various forms of nitrogen not determined by Kjeldahl procedures commonly employed for soil analysis. From this and other evidence presented it is concluded that very little, if any, of the nitrogen in the soils examined was in the form of highly refractory nitrogen compounds or of compounds containing N—N or N—O linkages.3. Results by the method of determining nitrogen in soils recommended by the Association of Official Agricultural Chemists were 10–37% lower than those obtained by other methods tested. Satisfactory results were obtained by this method when the period of digestion recommended was increased.4. Ammonium-N fixed by clay minerals is determined by the Kjeldahl method.5. Selenium and mercury are considerably more effective than copper for catalysis of Kjeldahl digestion of soil. Conditions leading to loss of nitrogen using selenium are defined, and difficulties encountered using mercury are discussed.6. The most important factor in Kjeldahl analysis is the temperature of digestion with sulphuric acid, which is controlled largely by the amount of potassium (or sodium) sulphate used for digestion.7. The period of digestion required for Kjeldahl analysis of soil depends on the concentration of potassium sulphate in the digest. When the concentration is low (e.g. 0·3 g./ml. sulphuric acid) it is necessary to digest for several hours; when it is high (e.g. 1·0 g./ml. sulphuric acid) short periods of digestion are adequate. Catalysts greatly affect the rate of digestion when the salt concentration is low, but have little effect when the salt concentration is high.8. Nitrogen is lost during Kjeldahl analysis when the temperature of digestion exceeds about 400° C.9. Determinations of the amounts of sulphuric acid consumed by various mineral and organic soils during Kjeldahl digestion showed that there is little risk of loss of nitrogen under the conditions usually employed for Kjeldahl digestion of soil. Acid consumption values for various soil constituents are given, from which the amounts of sulphuric acid likely to be consumed during Kjeldahl digestion of different types of soil can be calculated.10. Semi-micro Kjeldahl methods of determining soil nitrogen gave the same results as macro-Kjeldahl methods.11. The use of the Hoskins apparatus for the determination of ammonium is described.12. It is concluded that the Kjeldahl method is satisfactory for the determination of nitrogen in soils provided a few simple precautions are observed. The merits and defects of different Kjeldahl procedures are discussed.

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(Determination of Nitrogen in Shale Oil and Petroleum)Effects of Digestion Temperature on Kjeldahl Analyses

Cited by 51 publications

References 6 publications

Kjeldahl Method for Organic Nitrogen

Kjeldahl Method for Organic Nitrogen

Determination of Nitrogen

Determination of nitrogen in soil by the Kjeldahl method

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