Ammonia Nessler procedure

Ammonia and ammonium ions in industrial water streams, including waste-water streams, can be determined by either of two methods (ASTM Procedure D1426). In the first, the sample is buffered to a pH of 7.4 and distilled into a solution of boric acid where the ammonia nitrogen is deterrnined colorimetricaHy with Nessler reagents or titrated using standard sulfuric acid. 

Procedure Dissolve the specified quantity of the substance being examined in 40 ml DW, and transfer to a Nessler cylinder. Add to it 2 ml iron-free citric acid solution and 0.1 ml thioglycollic acid, mix, make alkaline with iron-free ammonia solution, dilute to 50 ml with DW and allow to stand for 5 minutes. Any colour produced is not more intense than the standard colour. 

Ammonia was determined by nesslerization, using a procedure taken from Higuchi (26) in which 2-ml. aliquots were mixed directly with reagents for color development and read at 426 mp. 

Procedure (Note Refer to Lead Limit Test, Appendix TTTR, for the solutions and the control.) Add 3 mL of Ammonium Citrate Solution and 0.5 mL of Hydroxylamine Hydrochloride Solution to the Sample Solution, and make the combined solutions alkaline to phenol red TS with ammonium hydroxide. Add 10 mL of Potassium Cyanide Solution. Immediately extract the solution with successive 5-mL portions of Dithizone Extraction Solution, draining off each extract into another separator, until the last portion of dithizone solution retains its green color. Shake the combined extracts for 30 s with 20 mL of 1 100 nitric acid, and discard the chloroform layer. Add exactly 4 mL of Ammonia-Cyanide Solution and 2 drops of Hydroxylamine Hydrochloride Solution to the acid solution. Add 10 mL of Standard Dithizone Solution, and shake the mixture for 30 s. Filter the chloroform layer through an acid-washed filter paper into a Nessler tube, and compare the color with that of a standard prepared as follows Add 0.25 mL of the Standard Lead Solution containing 10 p,g/mL of lead (Pb) ion, 4 mL of Ammonia-Cyanide Solution, and 2 drops of Hydroxylamine Hydrochloride Solution to 20 mL of 1 100 nitric acid, and shake for 30 s with 10 mL of Standard Dithizone Solution. Filter through an acid-washed filter paper into a Nessler tube. The color of the Sample Solution does not exceed that in the control. 

If, however, the precipitate of diphenylurea is too small to weigh accurately, it is converted to ammonia and determined colorimetrically by the Nessler method. In this procedure, the filter paper is removed from the funnel and placed in a small beaker 4 ml. pure sulphuric acid (66° Be) are added, allowing this to flow slowly over the platinum spiral and through the funnel so as to wash off all traces of adherent precipitate. To the mixture obtained in this way 10 mgm. mercuric sulphate are added and the whole is then kept near boiling temperature for 2 hours. After allowing to cool, 20 ml. distilled water are added and the mixture is transferred to a 200-ml. flask containing 0-25 gm. sodium thiosulphate dissolved in 100 ml. water to remove the mercury. The beaker is washed with water which is added to the contents of the flask until the total volume is about 150 ml. and the ammonia determined in this. 

Two-line and multiline manifolds are, of course, now commonplace for FIA methods. In fact, most of the procedures described in the FIA literature (Chapter 7) utilize this approach. Thus, in Ref. 52 is described a turbidimetric procedure for the determination of ammonia in low concentrations with the use of Nessler s reagent, while Ref. 253 recounts the spectrophotometric determination of chromium(VI). Besides being based on one-phase equilibria, multiline manifolds may also involve gas diffusion, solvent extraction, and liquid-liquid phase reactions in packed reactors (see the following sections). It should be emphasized, however, that a FIA system should always be kept as simple as possible, and that a well-designed chemical analysis will often require only the use of a two-line manifold. 

Pilone et al. (1991) have questioned the sensitivity of Nessler s reagent in detecting potentially low concentrations of ammonia produced from arginine initially present at concentrations described by Garvie (1967). Instead, they recommended that the concentration of the amino acid be increased from 0.3% to 0.6% (wt/vol). Using this increased concentration of L-arginine, they found that some strains of Leuc. oenos did, in fact, produce ammonia. The above procedure includes this recommendation. 

Analytical and Tast Methods. Numerous instrumental and chemical techniques are available for the determination of acrylonitrile. The method of choice is directed by the concentration and the medium involved. For direct assay of acrylonitrile, titrimetric procedures are frequently used. Dodecyl mercaptan reacts with acrylonitrile under base catalysis excess mercaptan is then hacktitrated with an acid bromate-iodide solution (63), or alternatively, for colored solutions, with silver nitrate (64). Hydrolysis of the nitrile with strong base generates ammonia, which can then be determined by Nessler s reagent (65). 

After this point, the conventional procedure is used in all cases distillation and photometric determination of the ammonia either using Nessler reagent or indophenol, or determination of ammonia by titration. 

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