Hydroxylammonium chloride

Sulphuric acid is added to the electrolyte and the hydroxylamine is formed as hydroxylammonium sulphate, (NH30H)2S04 [cf, (NHJjSOj. Addition of barium chloride then precipitates barium sulphate and hydroxylammonium chloride, (NH30H)C1, is obtained. 

The special reducing agent (a solution containing cupro-ammonia ions) is first prepared. Dissolve 63 g. of crystallised copper sulphate in 250 ml. of water in a 1-Utre heaker, add 100 ml. of concentrated ammonium hydroxide solution (sp. gr. 0-88), and cool the solution to 10°. Dissolve 17 8 g. of hydroxylammonium chloride or 21 g. of hydroxylammonium sulphate in 60 ml. of water, cool to 10°, and add 42 -5 ml. of QN sodium hydroxide solution if the resulting solution of tydroxylamine is not clear, filter it at the pump. Without delay add the hydroxylamine solution, with stirring, to the ammoniacal cupric sulphate solution. Reduction occurs at once, a gas is evolved, and the solution assumes a pale blue colour. Protect the reducing agent from the air if it is not used immediately. 

Anhydrous NH2OH can be prepared by treating a suspension of hydroxylammonium chloride in butanol with NaOBu ... 

Procedure. To 10.0 mL of the solution containing up to 200 fig of copper in a separatory funnel, add 5.0 mL of 10 per cent hydroxylammonium chloride solution to reduce Cu(II) to Cu(I), and 10 mL of a 30 per cent sodium citrate solution to complex any other metals which may be present. Add ammonia solution until the pH is about 4 (Congo red paper), followed by lOmL of a 0.1 per cent solution of neo-cuproin in absolute ethanol. Shake for about 30 seconds with 10 mL of chloroform and allow the layers to separate. Repeat the extraction with a further 5 mL of chloroform. Measure the absorbance at 457 nm against a blank on the reagents which have been treated similarly to the sample. 

Traces of many metals interfere in the determination of calcium and magnesium using solochrome black indicator, e.g. Co, Ni, Cu, Zn, Hg, and Mn. Their interference can be overcome by the addition of a little hydroxylammonium chloride (which reduces some of the metals to their lower oxidation states), or also of sodium cyanide or potassium cyanide which form very stable cyanide complexes ( masking ). Iron may be rendered harmless by the addition of a little sodium sulphide. 

Add 0.5g hydroxylammonium chloride (to prevent oxidation), and 3mL triethanolamine (to prevent precipitation in alkaline solution) use boiled-out (air-free) water. 

Determination of calcium. Pipette two 25.0 mL portions of the mixed calcium and magnesium ion solution (not more than 0.01M with respect to either ion) into two separate 250 mL conical flasks and dilute each with about 25 mL of de-ionised water. To the first flask add 4 mL 8 M potassium hydroxide solution (a precipitate of magnesium hydroxide may be noted here), and allow to stand for 3-5 minutes with occasional swirling. Add about 30 mg each of potassium cyanide (Caution poison) and hydroxylammonium chloride and swirl the contents of the flask until the solids dissolve. Add about 50 mg of the HHSNNA indicator mixture and titrate with 0.01 M EDTA until the colour changes from red to blue. Run into the second flask from a burette a volume of EDTA solution equal to that required to reach the end point less 1 mL. Now add 4 mL of the potassium hydroxide solution, mix well and complete the titration as with the first sample record the exact volume of EDTA solution used. Perform a blank titration, replacing the sample with de-ionised water. 

If the water contains traces of interfering ions, then 4 mL of buffer solution should be added, followed by 30 mg of hydroxylammonium chloride and then 50 mg analytical-grade potassium cyanide (Caution) before adding the indicator. 

Procedure. Prepare a manganese(II) sulphate solution (approx. 0.05M) by dissolving 11.15 g of the analytical-grade solid in 1 L of de-ionised water standardise the solution by titration with 0.05 M EDTA solution using solochrome black indicator after the addition of 0.25 g of hydroxylammonium chloride — see below. 

Pipette 25 mL of the solution containing magnesium, manganese and zinc ions (each approx. 0.02M), into a 250 mL conical flask and dilute to 100 mL with de-ionised water. Add 0.25 g hydroxylammonium chloride [this is to prevent oxidation of Mn(II) ions], followed by 10 mL of the buffer solution and 30-40 mg of the indicator/potassium nitrate mixture. Warm to 40 °C and titrate (preferably stirring magnetically) with the standard EDTA solution to a pure blue colour. 

Procedure. Dissolve a weighed amount of ferro-manganese (about 0.40 g) in concentrated nitric acid and then add concentrated hydrochloric acid (or use a mixture of the two concentrated acids) prolonged boiling may be necessary. Evaporate to a small volume on a water bath. Dilute with water and filter directly into a 100 mL graduated flask, wash with distilled water and finally dilute to the mark. Pipette 25.0 mL of the solution into a 500 mL conical flask, add 5 mL of 10 per cent aqueous hydroxylammonium chloride solution, 10 mL of 20 per cent aqueous triethanolamine solution, 10-35 mL of concentrated ammonia solution, about 100 mL of water, and 6 drops of thymolphthalexone indicator solution. Titrate with standard 0.05M EDTA until the colour changes from blue to colourless (or a very pale pink). 

In the back-titration small amounts of copper and zinc and trace amounts of manganese are quantitatively displaced from the EDTA and are complexed by the triethanolamine small quantities of cobalt are converted into a triethanolamine complex during the titration. Relatively high concentrations of copper can be masked in the alkaline medium by the addition of thioglycollic acid until colourless. Manganese, if present in quantities of more than 1 mg, may be oxidised by air and forms a manganese(III)-triethanolamine complex, which is intensely green in colour this does not occur if a little hydroxylammonium chloride solution is added. 

Discussion. This gravimetric determination depends upon the separation and weighing as elementary selenium or tellurium (or as tellurium dioxide). Alkali selenites and selenious acid are reduced in hydrochloric acid solution with sulphur dioxide, hydroxylammonium chloride, hydrazinium sulphate or hydrazine hydrate. Alkali selenates and selenic acid are not reduced by sulphur dioxide alone, but are readily reduced by a saturated solution of sulphur dioxide in concentrated hydrochloric acid. In working with selenium it must be remembered that appreciable amounts of the element may be lost on warming strong hydrochloric acid solutions of its compounds if dilute acid solutions (concentration <6M) are heated at temperatures below 100 °C the loss is negligible. 

Electrolysis of chloride solutions may be carried out provided that a sufficient amount (1 —5 g) of either hydrazinium chloride or of hydroxylammonium chloride is added as an anodic depolariser ... 

Hydroxylammonium chloride. 10 per cent aqueous solution, or benzene-1,4-diol (quinol), 1 per cent solution in an acetic acid buffer of pH ca 4.5 (mix 65 mL of 0.1M acetic acid and 35 mL of 0.1M sodium acetate solution). Prepare when required. 

The iron may also be reduced with hydroxylammonium chloride. Add 5 mL of the 10 per cent hydroxylammonium solution, adjust the pH of the slightly acid solution to 3-6 with sodium acetate, then add 4mL of the 1,10-phenanthroline solution, dilute to 50 mL, mix, and measure the absorbance after 5-10 minutes. 

To determine organically bound mercury, the sample is treated (500 ml) with 0.5 M sulfuric acid aqueous potassium permanganate and set aside for 24 h. Aqueous hydroxylammonium chloride is added and the determination completed as above. The amount of mercury in the samples is calculated by reference to the standard absorptions. Average recoveries of 0.05 xg mercury were 88%. 

Step 2 To the residue is added 40 mL of hydroxylammonium chloride, adjusted to the appropriate pH using nitric acid, and the extraction repeated as in step one. 

Vapours of mercury, phenyl, and alkylmercury compounds were collected and measured as described except that the dichromate absorption solution was analyzed by the mercury reduction technique [28] after treatment with an excess of chloride hydroxylammonium chloride solution. 

In a similar procedure [32] the sediment is wet oxidised with dilute sulphuric acid and nitric acids in an apparatus in which the vapour from the digestion is condensed into a reservoir from which it can be collected or returned to the digestion flask as required. The combined oxidised residue and condensate are diluted until the acid concentration is IN and nitrate is removed by addition of hydroxylammonium chloride with boiling. Fat is removed from the cooled solution with carbon tetrachlodithizone in carbon tetrachloride. The extract is shaken with 0.1M hydrochloric acid and sodium nitrite solution and, after treatment of the separated aqueous layer with hydroxylammonium chloride a solution of urea and then EDTA solution are added to prevent subsequent extraction of copper. The liquid is then extracted with a 0.01% solution of dithizone in carbon tetrachloride and mercury estimated in the extract spectrophotometrically at 485nm. 

B. 1,2-Cyclohexanedionedioxime has been prepared by oxi-mating 1,2-cyclohexanedione with hydroxylammonium chloride in aqueous potassium hydroxide solution 3 6 by oximating 2-iso-nitrosocyclohexanone with hydroxylammonium chloride 7 8 and by oximating sodium 2-isonitrosocyclohexanone with hydroxylammonium chloride in methanolic solution.6... 

The step 2 product (12.41 mmol) dissolved in 10 ml (V -dimethylacetamide was treated with a mixture of hydroxylammonium chloride (2.90 mmol) and sodium acetate (2.90 mmol) dissolved in 5 ml water and then stirred at 100°C for 4 hours. The mixture was treated with water and a brownish yellow solid isolated. This material was washed with water, dissolved in CH2C12, and dried using MgS04. It was concentrated, repurified by precipitation in CH2Cl2/hexane solution, and 0.81 g product isolated. 

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