Nitroso-naphthol solution

Nitroso-naphthol solution. Spray the plate with the reagent, then spray with a 10% v/v solution of hydrochloric acid and heat at 110° for 20 minutes. Blue-black spots on a yellow background are given by ergot alkaloids. 

The reagent consists of a 1 per cent solution of a-nitroso-/ -naphthol in 50 per cent acetic acid, or in ethanol, or in acetone. 

Chloroform is the most popular solvent, although carbon tetrachloride, benzene, toluene, and isoamyl acetate are also used. The reaction between cobalt ions and nitroso-naphthols takes place in weakly acidic medium and proceeds rather slowly. For this reason, the sample solution is allowed to stand for about 30 min after the reagent is added, before the complex is extracted. The reaction with cobalt is done at pH 3 with l-nitroso-2-naphthol, and at pH 4 with 2-nitroso-l-naphthol. 

The cobalt complex formed is stable and does not decompose even when treated with 2 M HCl, which decomposes other complexes formed in a weakly acidic medium, e.g., those of Ni, Cu, Fe, and Cr. Uncomplexed nitroso-naphthol is scrubbed from the organic extract with NaOH solution. 

To a solution containing not more than 30 pg of Co, add 1 ml of the 1-nitroso-2-naphthol (or 2-nitroso-l-naphthol) solution with stirring, adjust the pH of the solution with ammonia to 4 (or 5 in the case of 2-nitroso-l-naphthol), and allow to stand for 30 min. Transfer the solution to a separating funnel and extract with two portions of CHCI3. Shake the combined extracts with 2 M HCl, followed by two portions of 2 M NaOH, and finally wash with water. Transfer the extract to a 25-ml standard flask, make up to the mark with chloroform, and measure the absorbance of the solution at 415 nm (in the case of 2-nitroso-l-naphthol, at 365 nm), using the solvent as the reference. 

To a 1001 sample, 500 ml of 12 mol 1 hydrochloric acid, 10 ml of cobalt carrier solution (Img Co mH ), and 400 ml of l-nitroso-2-naphthol solution (5mgmH in ethanol) are added. With peristaltic pumps, the sample solution, 1 mol 1 aqueous ammonia, and anionic surfactant solution (O.SmgmH in 70% ethanol, sodium oleate-SDS = 1 3) are fed into a 11 reaction bottle at flow rates of 500, 35, and 10 ml min respectively. In the reaction bottle, the cobalt chelate is captured by a flocculent precipitate of indium hydroxide at pH 8.5-9. The contents of the bottle are continuously transferred to a flotation cell and flotation continues until the completion of sample feeding. The precipitate is sucked into a sampling bottle and then dissolved in 100 ml of 6molH hydrochloric acid. The cobalt chelate is separated from indium ions by extraction with chloroform and destroyed by dry oxidation. After dissolving the residue in 5 ml of 8 mol 1 hydrochloric... 

Procedure. A drop of bromine water is placed on the metal surface and allowed to stand until the bromine color is nearly discharged. Then a drop of a freshly prepared 1 % solution of a-nitroso- -naphthol in 50 % acetic acid is added. If cobalt is present, a brown-red precipitate appears at once. 

Treatment of a solution of sodium nitrite and the sodium salt of p-naphthol with sulphuric acid gives an excellent jdeld of a-nitroso- p-naphthol ... 

Nitroso-/S-naphthol, HOCjoHjNO—saturated solution saturate 100 mL of 50% acetic acid with the solid. 

The only practical method of preparing 1,4-aminonaphthol is from a-naphthol through an azo dye, the nitroso compound not being readily available. The majority of investigators have reduced technical Orange I with stannous chloride Mi.is.is.ir.is by the procedures discussed above, and benzeneazo-a-naphthol has been reduced by the same reagent. In order to make possible the use of crude, technical a-naphthol a method has been developed for the preparation of the benzeneazo compound, its separation from the isomeric dye coming from the d-naphthol present as well as from any disazo compound by extraction with alkali, and the reduction of the azo compound in alkaline solution with sodium hydrosulfite. The process, however, is tedious and yields an impure product. 

Procedure. Prepare the 2-nitroso-l-naphthol reagent by dissolving 1.0 g of the solid in 100 mL of glacial acetic acid. Add 1 g of activated carbon shake the solution before use and filter off the required volume. 

In yet another experiment, three set of 25 ml of 100 ppm NiS04 solutions were complexed with 0.1 ml of 1% l-Nitroso-2-Naphthol and sonicated for 10, 20 and 30 min and compared with a control sample which was stirred mechanically. Turbidity of these solutions was measured. From the Table 9.9, it is clear that the turbidity of the solution increased as the time of sonication increased. 

In another procedure [522] the sample of seawater (0.5-3 litres) is filtered through a membrane-filter (pore size 0.7 xm) which is then wet-ashed. The nickel is separated from the resulting solution by extraction as the dimethylglyoxime complex and is then determined by its catalysis of the reaction of Tiron and diphenylcarbazone with hydrogen peroxide, with spectrophotometric measurement at 413 nm. Cobalt is first separated as the 2-nitroso-1-naphthol complex, and is determined by its catalysis of the oxidation of alizarin by hydrogen peroxide at pH 12.4. Sensitivities are 0.8 xg/l (nickel) and 0.04 xg/l (cobalt). 

Nitroso-/3-naphthol has been made by the action of hydroxyl-amine hydrochloride on /3-naphtho-quinonc-chlorimide 1 by the action of sulfuric acid upon a solution of potassium or sodium nitrite and the sodium salt of /3-naphthol 2 by the action of sodium nitrite upon an alcoholic solution of zinc chloride and /3-naphthol 3 by the action of sodium nitrite upon /3-naphthol suspended in zinc sulfate solution 4 by the action of nitrous acid on /3-dinaphthol methane 6 and by the action of nitrosyl sulfate upon the sodium salt of /3-naphthol.6... 

It is usually not convenient to dry the nitroso-/3-naphthol. The amount given in these directions corresponds to 200 g. of /S-naphthol and the yield is calculated on this basis. The nitroso-/3-naphthol dissolves in one mole of sodium hydroxide, forming a green solution. There is left in suspension a small amount of amorphous brown material which it is unnecessary to remove. 

If the phenol is allowed to react with nitrous acid (generated in an acidified solution of sodium nitrite), the nitrosophenol may be obtained in good yield. An example is provided by the nitrosation of 2-naphthol which yields l-nitroso-2-naphthol (Expt 6.103). 

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