Nitrites in water

Solution B Dissolve 10 g sodium nitrite in water and make up to 100 ml. 

It was found that when a-tocopherol was dispersed in the aqueous phase in absence of the oil, nitrite was readily destroyed. It was concluded that the reduced inhibition obtained with butylated hydroxyanisole and a-tocopherol was at least in part due to their isolation from the nitrite in water phase. On the other hand, the reducing portion of the ascorbyl palmitate molecule could be in the water phase at the oil/water interface. 

Co. and 20 mM nitrite in water, pH 3, 25 C, 60 min reaction], it was nitrosated to yield 3.62 mM 2,6-dimethyl-N-nitrosomorpho-line (DMNM), which was a 10% greater yield than that for a similar nitrosation of morpholine to give NMOR. This indicated a slightly larger rate constant for DMNM than for NMOR formation (3). Crude DMM is a 2 1 mixture of the cis and trans isomers ( 0). GC analysis of the product of the kinetic run showed that the 2 isomers were nitrosated at similar rates. Cis-DMNM [retention time (RT), 320 sec] was well separated from NMOR (RT, 430 sec), but trans-DMNM (RT, 405 sec) was not. Accordingly, we prepared pure cis-DMM, b.p. 133 C, by spinning-band fractional distillation of crude DMM and used it in the analytical procedure. The RT of N-nitrosopyrrolidine (NPYR) was 390 sec. 

Standard addition should be carried out to assess recovery. In doing so, the variation in concentration due to other phenomena is avoided. As an example, Guan" reports 51% recovery for nitrite in water due to rapid oxidation of the analyte. 

In order to prepare the Pauly reagent two solutions, solution I (0.4 M sodium sulfanilate in water) and solution II (0.4 M sodium nitrite in water) are made separately. Just before use, solution I with solution II, 0.25 M HC1, and 2 M NaOH (1 1 8 10) are mixed successively. This solution, which is not stable, should be applied as a spray within minutes and discarded. The ninhydrin test will not interfere with the Pauly reagent. 

To 10 ml of 6N hydrochloric acid is added 0.28 gm (1.25 mmole) of 2-(2-aminophenyl)-5-methylbenzotriazole. The solution is cooled to 0°C and diazotized by the addition of 0.10 gm (1.45 mmole) of sodium nitrite in water. After stirring for 15 min, 0.18 gm (2.5 mmole) of sodium azide in water is added. The reaction mixture is allowed to stand for 3 hr, then filtered the solid... 

Potassium-ynitraminotetrazole, KCHN602, mw 168.17, N 49.98%, was obtained as almost colorless plates on treating nitramino-guanidine with K nitrite in water, as described in Ref 2,p 2328. The compd exploded with a purple flash when dropped on a hot... 

Quantitative Determination. — Dissolve 1.5 gm. of silver nitrite in water and dilute to 500 cc. Make a mixture containing 18 to 19 cc. of decinormal potassium permanganate solution, 20 cc. of dilute sulphuric acid, and 300 cc. of water, heat it to 40 to 50° C., and run the nitrite solution into it until the pink color just disappears. Care must be taken towards the end to introduce the nitrite solution very slowly, because the change from pink to colorless always requires some time. 

Diazotise 32 g (0.25 mol) of o-chloroaniline in the presence of 40 ml of concentrated hydrochloric acid and 22.5 ml of water in the usual manner (compare Expt 6.70) with a concentrated solution of 18.5 g sodium nitrite in water. Transfer the cold, filtered diazonium solution to a 1.5-litre bolt-head flask surrounded by ice-water, introduce 500 ml of cold benzene (CAUTION), stir vigorously and add a solution of 80 g of sodium acetate trihydrate in 200 ml of water dropwise, maintaining the temperature at 5-10 °C. Continue the stirring for 48 hours after the first 3 hours, allow the reaction to proceed at room temperature. Separate the benzene layer, wash it with water and remove the benzene by distillation at atmospheric pressure distil the residue under reduced pressure and collect the 2-chlorobiphenyl at 150-155 °C/10mmHg. The yield is 18 g (76%). Recrystallise from aqueous ethanol m.p. 34 °C. 

A stirred and cooled (0°C) solution of l-(2,4-diaminophenyl)-l-ethanone in a concentrated hydrochloric acid solution, water and acetic acid was diazotated with a solution of sodium nitrite in water. After stirring at 0°C, the whole was poured onto a solution of copper (I) chloride in a concentrated hydrochloric acid solution while stirring. The mixture was heated at 60°C. After cooling to room temperature, the product was extracted twice with 2,2 -oxybispropane. The combined extracts were washed successively with water, a diluted sodium hydroxide solution and again twice with water, dried, filtered and evaporated, yielding l-(2,4-dichlorophenyl)-l-ethanone. 

The work of Mosko [116] is important in that he is one of the few workers who have given serious consideration to the determination of nitrite in water. His paper is concerned with the determination of chloride, sulphate, nitrate, nitrite, orthophosphate, fluoride and bromide in industrial effluents, waste water and cooling water. Two types of analytical columns were evaluated (standard anion and fast run series). Chromatographic conditions, sample pretreatment and the results of interference, sensitivity, linearity, precision, comparative and recovery studies are described. The standard column provided separation capabilities which permitted the determination of all seven anions. The fast run column could not be used for samples containing nitrite or bromide owing to resolution problems. 

This technique has been applied by Iskandami and Petrzyk [316] to the determination of nitrate and nitrite in water. Chemically bonded amine materials have been used to remove interference by humic substances prior to the ion chromatographic determination of nitrate and sulphate in non saline waters. 

Davenport and Johnson [30] used ion exchange chromatography on Amberlite IRA-900 strongly basic resin to determine nitrate and nitrite in water. 0.10M perchloric acid was used as eluent and an electrochemical cadmium electrode detector was used. 

Derivatisation-electron capture gas chromatography has been used to determine pg L 1 quantities of nitrite in water without interference from halides, nitrate, phosphate, sulphate, bicarbonate, ammonium and alkali metals and alkaline earth metals [792],... 

Nitrates and nitrites in water are frequently estimated together, e.g. by reduction to ammonia,1 which can be determined m the manner described below alternative processes are based on the reduction of these salts to nitric oxide which may be measured volumetrically, and on reduction of the nitrate to nitrite when the total nitrite may be estimated eolonmetncaUy by the addition of sulphanihc acid and a-naphthylamine.3 For the estimation of nitrites and mtrates separately, organic colorimetric methods are usually applied.4... 

Deamination of phenosafranin with sulfuric acid and sodium nitrite in water gives 5-phenyl-phenazinium chloride. ... 

The pieces of paper with 3-hydroxykynurenine, 3-hydroxyanthranilic acid, and xanthurenic acid are each placed in an Erlenmeyer flask fitted with a ground-glass stopper and containing 3.8 ml distilled water. After 15-16 hours, 1 ml diazotized sulfanilic acid (0.5% in 2% hydrochloric acid mixed immediately before using with an equal volume of 0.5% solution of sodium nitrite in water) and 0.2 ml pyridine are added. The temperature must be held constant at 15° to obtain reproducible results. The color resulting from xanthurenic acid is read immediately at 510 mp, and of the other two derivatives after 60-80 minutes at 450 mp. 

The diazotization of aminopyrazines has been described in earlier sections. Section V.IH records the preparation of 2-fluoropyrazine from 2-aminopyrazine in fluoroboric acid containing copper powder with sodium nitrite (882, 884) and Section V.ll the preparation of iodopyrazines from some aminopyrazines via isodiazotate salts (30) (887). These salts were assigned the isodiazotate structure, on the basis of their inability to couple with 0-naphthol in alkaline solution (887) and they were characterized by hydrolysis in cold 40% aqueous sulfuric acid to the hydroxypyrazine (887). Section V.I K describes the conversion of aminopyrazines to bromopyrazines (798, 800, 807, 890-892) for example, 2-amino-3-methoxy-carbonylpyrazine with hydrobromic acid, bromine, and sodium nitrite in water gave 2-bromo-3-methoxycarbonylpyrazine (798, 890). The diazotization of aminopyrazines to hydroxypyrazines has been described in Section VI. 1C, to alkoxy-pyrazines in Section V1.3C, and to oxopyrazines in Section V1.9A(5). 2-Amino-pyrazine with isopentyl nitrite in benzene gave 2-phenylpyrazine (45%) and some 2-isopentoxypyrazine and 2,2 -dipyrazinyl amino isomers (1211). 

Reagent for Nitrites in Water.— An illustration of such a reaction is one which is the basis of the colorimetric determination of nitrites in water. When sulphanilic acid, para-amino benzene sulphonic acid, is diazotized and the resulting diazo compound treated with alpha-naphthylamine the benzene ring and the naphthalene ring become coupled as an azo compound which is red in color. 

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