Microdetermination of Nitrogen in Organic Compounds

Alford, William C.

doi:10.1021/ac60065a033

Cited by 27 publications

(3 citation statements)

References 20 publications

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“…While searching for a modification which would improve the analysis of refractory compounds, several oxidation aids recommended by other workers (1,9,13,14,(16)(17)(18) were tried. Some oxidation aids did not improve the results at all.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of an Automatic Nitrogen Analyzer for Tractable and Refractory Compounds.

Sternglanz¹,

Kollig²

1962

Anal. Chem.

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If the acidity of the solution is too high, the amine is also protonated to a great extent and cannot add to the protonated aldehyde. If the acid concentration is too low, not enough of the aldehyde is protonated to cause a significant rate of addition of the amine.Samples of n-butylamine mixed with equimolar quantities of di-n-butylamine, tri-n-butylamine, and ammonia were titrated according to this procedure, and no interference due to the presence of these added bases was noticed. The results of the titration of the above mixtures were all within two standard deviations of the mean of the results of n-butylamine alone.Repeated attempts were made to titrate primary aliphatic amines in the presence of primary aromatic amines without success. Although the aromatic amines do not react appreciably with %ethylhexanal under the reaction conditions employed for the titration, the intrinsic ultraviolet absorbance of the aromatic amines a t 305 mp causes the absorbance of the solution being titrated to be so great that the relative change in absorbance during titration is very small. A number of aromatic aldehydes were tried as titrants, but none of these reacted rapidly enough with the aliphatic amines to make a practical titration possible.Crotonaldehyde, Lvhose carbonyl absorption peak is a t 325 mp instead of 295 mM, was also tried as a titrant, but unfortunately crotonaldehyde reacts to a significant extent with many aromatic amines while reacting only slowly with most aliphatic amines. Thus, the procedure reported can tolerate the presence of only a small amount of an aromatic amine or any other substance whose intrinsic absorbance at 305 mp is high.

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Section: Discussionmentioning

confidence: 99%

Evaluation of an Automatic Nitrogen Analyzer for Tractable and Refractory Compounds.

Sternglanz¹,

Kollig²

1962

Anal. Chem.

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“…Table VII indicates that no significant losses of platinum occurred during cupellation. Difference in the bead size did not appear to be an important variable, but larger losses to the cupel were recorded when the ratio of platinum to silver was reduced to 20 to 1 and 10 to 1. The results with these small beads (10 mg.) are of interest because they are used in spectrographic determinations of the platinum metals in ores and concentrates.…”

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confidence: 86%

Modified Micro-Dumas Procedure for Determining Nitrogen

Childs¹,

Meyers²,

Johnston³

et al. 1956

Anal. Chem.

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“…It is commonly assumed that the Dumas method is superior to the Kjeldahl method in that it is of universal applicability, but there is no basis for this assumption. The customary Dumas methods fail with many compounds, particularly heterocyclic compounds, which tend to form nitrogenous chars that are difficult to burn (see Alford, 1952). The Kjeldahl methods commonly used also fail with certain compounds, but numerous modifications of these methods have been developed which greatly extend the scope of Kjeldahl's (1883) original technique.…”

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confidence: 99%

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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Microdetermination of Nitrogen in Organic Compounds

Cited by 27 publications

References 20 publications

Evaluation of an Automatic Nitrogen Analyzer for Tractable and Refractory Compounds.

Evaluation of an Automatic Nitrogen Analyzer for Tractable and Refractory Compounds.

Modified Micro-Dumas Procedure for Determining Nitrogen

Determination of nitrogen in soil by the Kjeldahl method

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