Nitroso-R-salt

For colorimetric or gravimetric determination l-nitroso-2-naphthol can be used. For chromatographic ion exchange (qv), cobalt is isolated as the nitroso-(R)-salt complex. The cyanate complex is used for photometric determination and the thiocyanate for colorimetry. A rapid chemical analysis of... 

Co (II) with nitroso-R-salt on the bases of gelatin film ... 

Discussion. An excellent method for the colorimetric determination of minute amounts of cobalt is based upon the soluble red complex salt formed when cobalt ions react with an aqueous solution of nitroso-R-salt (sodium 1-nitroso-2-hydroxynaphthalene-3,6-disulphonate). Three moles of the reagent combine with 1 mole of cobalt. 

Procedure. The test solution should contain between 0.001 and 0.02 mg of cobalt. Evaporate almost to dryness, add 1 mL of concentrated nitric acid, and continue the evaporation just to dryness to oxidise any iron(II) which may be present. Dissolve the residue in 10 mL of water containing 0.5 mL each of 1 1 hydrochloric acid and 1 10 nitric acid. Boil for a few minutes to dissolve any solid material. Add 2.0 mL of a 0.2 per cent aqueous solution of nitroso-R-salt and also 2.0 g of hydrated sodium acetate. The pH of the solution should be close to 5.5 check with bromocresol green indicator or with a pH meter. Boil for 1 minute, add 1.0 mL of concentrated hydrochloric acid, and boil again for... 

Cupferron Nitroso-R-salt 688 Nitrous acid removal of. 514 Nonaqueous titrations 307 indicators for, 284 solvents for. 283... 

Samples of metal complexes isolated from the final solutions were subjected to microanalysis (for carbon, hydrogen, oxygen, and sulfur). Metals were determined colorimetrically by the following methods— copper as the complex formed with sodium diethyl dithiocarbamate (6) cobalt as the nitroso-R salt complex (7) nickel as the dimethylglyoxime complex (4). 

Nitroso-R-salt see l-nitroso-2-naphthol-3,6-disulphonic acid, disodium salt, hydrate. 

Nitroso-R-salt, n82 Nitroterephthalic acid, n31 2-Nitro-p-toluidine, m317 4-Nitro-e>-toluidine, m315... 

B. Fuse about 1 mg of sample with about 50 mg of potassium pyrosulfate in a porcelain crucible, cool, and break up the mass with a glass rod. Add 3 mL of water, and dissolve by boiling. Add 1 drop of phenolphthalein TS, mix, and then add drops of a 1 10 solution of sodium hydroxide until just pink. Add 500 mg of sodium acetate, 0.5 mL of 1 N acetic acid, and 0.5 mL of a 1 500 solution of nitroso R salt. A red or orange-red color appears at once. Add 0.5 mL of hydrochloric acid, and boil for 1 min. The red color persists. 

Sodium 1-nitroso-2-hydroxynaphthalene-3 6-disulphonate (nitroso-R-salt) reagent... 

The reagent consists of a 1 per cent solution of nitroso-R-salt in water. 

Sodium l-nitroso-2-hydroxy-naphthalene-3,6-disulphonate (1 %). Dissolve 1 g sodium l-nitroso-2-hydroxynaphthalene-3,6-disulphonate [Nitroso R-salt, Cl0H4(OH)(SO3Na)2NO] in 100 ml of water. 

A solid chelating material, l-nitroso-2-naphthol supported on silica gel, provides a rapid and highly selective mean of separating traces of Co(II) from natural waters [19]. Open-cell polyurethane foam loaded with PAN azo reagent [20], and organic resins modified with nitroso-R salt have been used similarly [21,22]. 

The thiocyanate method is suitable for the determination of relatively large amounts of cobalt. Methods with nitroso-naphthols or nitroso-R salt are specific but not very sensitive. An example of a really sensitive method is that using the azo reagent, 5-Br-PADAP. 

Nitroso-R salt (formula 18.3) is a derivative of l-nitroso-2-naphthol. Both reagents are specific for cobalt. The sulphonate groups in the molecule of nitroso-R salt render this reagent and its cobalt complex soluble in water but insoluble in non-polar solvents. Hence, nitroso-R salt is used to determine cobalt spectrophotometrically in aqueous medium [29]. In acidic solution (pH 4), cobalt(Il) is oxidized to Co(IlI). 

In acid solution, the reagent is yellow whereas the complex is red. Figure 18.2 shows the absorption spectra. The molar absorptivity of the red cobalt-nitroso-R salt complex at Xmax = 415 nm is 3.5-10" (a = 0.60). At 500 nm, where interference from the colour of the reagent is negligible, e= 1.5-10. ... 

The absorbance of the Co(III) complex solution may be measured with higher sensitivity at 415-425 nm, or with lower sensitivity at 500-520 nm (a reagent blank, or water as reference). The reaction of cobalt with nitroso-R salt is usually done in a hot weakly acidic medium buffered with sodium acetate. The solution is then made sufficiently acidic with hydrochloric or nitric acid to decompose the nitroso-R salt complexes of other metals (e.g., Cu, Ni, Fe, and Mn), which are less stable than the cobalt(III) complex. Phosphate or fluoride masks iron (III), which has a yellow colour in hydrochloric acid medium. 

Fig. 18.2. Absorption spectra of nitroso-R salt (vs. water) (1) and of its complex with cobalt (vs. the reagent) (2)...

When the colour reaction takes place in the presence of relatively large amounts of metals which also react in weakly acidic medium with nitroso-R salt, a considerable amount of the reagent should be added to the solution. 

The anionic cobalt-nitroso-R salt complex has been extracted with a (5-1-1) mixture of chloroform with butanol in the presence of TP. The extract contains an ion associate of composition corresponding to Co R CP = 1 3 6 (e = 5.0T0" at 510 nm) [30]. 

Nitroso-R salt, 0.1% solution. Store the solution in an amber-glass bottle. 

Cobalt has been determined by means of the nitroso-R salt in biological materials [1], natural waters [13], plants [101,102], iron ores [103], uranium minerals [15], cast iron and... 

Various other organic reagents have been proposed for determining Rh, viz. nitroso-R salt [57,58], 1,5-diphenylcarbazide [59], Chrome Azurol S (in the presence of CP) (e = 6.2-10" ) [60], and Chrompyrazole I in the presence of SnCl2 [61]. Rhodanine derivatives have been used for determination of Rh in the presence of Pd [62] and heavy metals [63]. 

Solid-phase extraction of various analyte complexes on e.g. microcrystalline naphthalene (Ni [23] and Cu [24] with nitroso-R salt and tetradecyldimethylbenzylammonium chloride), ammonium tetraphenylborate-naphthalene (U with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol) [25], chitin column (Cr(VI) with 1,5-diphenylcarbazide) [26], strong anion-exchange cartridge (Cr(VI) at pH 8) [27], Cig cartridge (CL-azo dye) [28] and minicolumn (As with ammonium diethyl dithiophosphate) [29], silica modified chemically with A-allyl- or A-phenyl-TV -propylthiourea (OSO4) [30] and Sephadex DEAE A-25 (chloride form) (V with Eriochrome Cyanine R) [31] prior to the spectrophotometric determination has recently been reported. The application of solid-phase spectrophotometry to determine nitrite and nitrate in water samples has recently been described [32]. 

Pyridylazo)resorcinol 4-(2-Pyridylazo)resorcinol + Tetradecyldimethyl-benzylammonium chloride 4-(2-Pyridylazo)resorcinol + Hydrogen peroxide Cobalt Nitroso-R salt... 

Co l-Nitroso-2-napKthol, 2-Nitroso-l-naphthol, nitroso-R salt, 5-CI-PADAB, NaDDC, PAN ... 

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