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% nitrogen2 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 linkages3 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 increased4 Ammonium-N fixed by clay minerals is determined by the Kjeldahl method5 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 discussed6 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 digestion7 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 (eg 0·3 g/ml sulphuric acid) it is necessary to digest for several hours; when it is high (eg 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 high8 Nitrogen is lost during Kjeldahl analysis when the temperature of digestion exceeds about 400° C9 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 calculated10 Semi-micro Kjeldahl methods of determining soil nitrogen gave the same results as macro-Kjeldahl methods11 The use of the Hoskins apparatus for the determination of ammonium is described12 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

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0021859600021572

Determination of nitrogen in soil by the Kjeldahl method

Nitrogen—Total 1

Influence of mineral matter on biomass pyrolysis characteristics

Total Nitrogen 1

Monomeric acrylamide is an important industrial chemical primarily used in the production of polymers and copolymers. It is also used for producing grouts and soil stabilizers. Acrylamide's neurotoxic properties have been well documented. This review will focus on pertinent information concerning other, non-neurotoxic, effects observed after exposure to acrylamide, including: its genotoxic, carcinogenic, reproductive, and developmental effects. It will also cover its absorption, metabolism, and distribution. The data show that acrylamide is capable of inducing genotoxic, carcinogenic, developmental, and reproductive effects in tested organisms. Thus, acrylamide may pose more than a neurotoxic health hazard to exposed humans. Acrylamide is a small organic molecule with very high water solubility. These properties probably facilitate its rapid absorption and distribution throughout the body. After absorption, acrylamide is rapidly metabolized, primarily by glutathione conjugation, and the majority of applied material is excreted within 24 h. Preferential bioconcentration of acrylamide and/or its metabolites is not observed although it appears to persist in tests and skin. Acrylamide can bind to DNA, presumably via a Michael addition-type reaction, which has implications for its genotoxic and carcinogenic potential. The available evidence suggests that acrylamide does not produce detectable gene mutations, but that the major concern for its genotoxicity is its clastogenic activity. This clastogenic activity has been observed in germinal tissues which suggest the possible heritability of acrylamide-induced DNA alterations. Since there is 'sufficient evidence' of carcinogenicity in experimental animals as outlined under the U.S. EPA proposed guidelines for carcinogen risk assessment, acrylamide should be categorized as a 'B2' carcinogen and therefore be considered a 'probable human carcinogen.' The very limited human epidemiological data do not provide sufficient evidence to enable one to judge the actual carcinogenic risk to humans. Acrylamide is able to cross the placenta, reach significant concentrations in the conceptus and produce direct developmental and post-natal effects in rodent offspring. It appears that acrylamide may produce neurotoxic effects in neonates from exposures not overtly toxic to the mothers. Acrylamide has an adverse effect on reproduction as evidenced by dominant lethal effects, degeneration of testicular epithelial tissue, and sperm-head abnormalities.

Al Steyermark

Papers

The condensed chemical dictionary. 10th ed

Spectrometric identification of organic compounds. Third edition

Recommended Specifications for Microchemical Apparatus. Micro-Kjeldahl Nitrogen

Report on Recommended Specifications for Microchemical Apparatus

Report on Recommended Specifications for Microchemical Apparatus