Nitrogen in organic substances

Ammonia may be estimated by dissolving the gas in a known volume of standard acid and then back-titrating the excess acid. In a method widely used for the determination of basic nitrogen in organic substances (the Kjeldahl method), the nitrogenous material is converted into ammonium sulphate by heating with concentrated sulphuric acid. The ammonia is then driven off by the action of alkali and absorbed in standard acid. 

Dumas method analychem A procedure for the determination of nitrogen in organic substances by combustion of the substance. dti-ma. meth-od dunnite See ammonium picrate. da.nTt)... 

The Lassaigne procedure for detecting nitrogen in organic compounds frequently gives unsatisfactory results with explosive compounds (diazonium salts, polynitro compounds and the like) and with certain volatile nitrogenous substances, such as bases, their acyl derivatives or their salts. These difficulties... 

A chemical element. High phosphorus content, combined with nitrogen and organic substances, can cause increased biological activity in water, known as eutrophication, which diminishes the oxygen supply. 

The nitrate reduction is an important process, since it facilitates the entrance of NO3 into the plant metabolism. The resorbed ammonia nitrogen, urea nitrogen and amino acids can be easily utilized by the plants. Nitrates accepted are used for the synthesis of nitrogen-containing organic substances only after their reduction to ammonia. This reduction is sensitive to the environmental conditions. In the case of a lack of saccharides as energy sources, or if the activity of the reductases is lessened, nitrate nitrogen can be accumulated in plant tissues. 

Proteins are nitrogen-containing organic substances which occur in the protoplasm of all plant and animal cells (Hare, 1969). The composition of proteins varies with the source, but a general range for protein composition can be deduced (Table 3.8) with other elements, for example, phosphorous (nucleoproteins) and iron (hemoglobin) also being present in trace amounts in certain proteins. 

The nitrogen contained in organic substances in water is converted to ammonium ions by KjeldahEs decomposition method. The ammonium ions are distilled from alkaline solution as ammonia, collected in boric acid solution and determined acidimetrically or photometrically in the receiver. Ammonium ions originally contained in the sample are separated, identified and deducted, or separated off by distillation before carrying out the Kjeldahl decomposition. Nitrite and nitrate are volatilized by H2SO4 in the... 

Because of the difficult accessibility of 1,5-diaminotetrazole (DAT, Fig. 8), only few synthetic methods for its preparation have been described in the literature. This compound, as all aminotetrazoles, has the highest content of nitrogen among organic substances (about 84%) and due to the aromaticity, it exhibits a relatively high thermal stability. 

Kjeldahl s method A method used for the determination of nitrogen in organic compounds. The nitrogenous substance is converted to ammonium sulfate by boiling with concentrated sulfuric acid (often with a catalyst such as CUSO4) in a specially designed long-necked Kjeldahl flask. The mixture is then made alkaline and the ammonia distilled off into standard acid for measurement by titration. It is named for the Danish chemist Johan Kjeldahl (1849-1900). 

The table below gives the lowest temperature that can be obtained from a mixture of the inorganic salt with finely shaved dry ice. With the organic substances, dry ice (—78°C) in small lumps can be added to the solvent until a slight excess of dry ice remains or liquid nitrogen (—196°C) can be poured into the solvent until a slush is formed that consists of the solid-liquid mixture at its melting point. 

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