Iron reductors

The amount of Fe in a 0.4891-g sample of an ore was determined by a redox titration with K2Cr20y. The sample was dissolved in HCl and the iron brought into the +2 oxidation state using a Jones reductor. Titration to the diphenylamine sulfonic acid end point required 36.92 mL of 0.02153 M K2Cr20y. Report the iron content of the ore as %w/w FeyOy. 

Discussion. Copper(II) ions are quantitatively reduced in 2M hydrochloric acid solution by means of the silver reductor (Section 10.140) to the copper(I) state. The solution, after reduction, is collected in a solution of ammonium iron(III) sulphate, and the Fe2+ ion formed is titrated with standard cerium(IV) sulphate solution using ferroin or AT-phenylanthranilic acid as indicator. 

Procedure (copper in crystallised copper sulphate). Weigh out accurately about 3.1 g of copper sulphate crystals, dissolve in water, and make up to 250 mL in a graduated flask. Shake well. Pipette 50 mL of this solution into a small beaker, add an equal volume of ca AM hydrochloric acid. Pass this solution through a silver reductor at the rate of 25 mL min i, and collect the filtrate in a 500 mL conical flask charged with 20 mL 0.5M iron(III) ammonium sulphate solution (prepared by dissolving the appropriate quantity of the analytical grade iron(III) salt in 0.5M sulphuric acid). Wash the reductor column with six 25 mL portions of 2M hydrochloric acid. Add 1 drop of ferroin indicator or 0.5 mL N-phenylanthranilic acid, and titrate with 0.1 M cerium(IV) sulphate solution. The end point is sharp, and the colour imparted by the Cu2+ ions does not interfere with the detection of the equivalence point. 

Carry out a blank determination, preferably before passing the iron solution through the reductor, by running the same volumes of acid and water through the apparatus as are used in the actual determination. This should not amount to more than about 0.1 mL of 0.02M permanganate, and should be deducted from the volume of permanganate solution used in the subsequent titration. 

It must be emphasised that if hydrochloric acid has been employed in the original solution of the iron-bearing material, the volume should be reduced to ca 25 mL and then diluted to ca 150mL with 5 per cent sulphuric acid. The determination is carried out as detailed above, but 25 mL of Zimmermann-Reinhardt or preventive solution must be added before titration with standard potassium permanganate solution. For the determination of iron in hydrochloric acid solution, it is more convenient to reduce the solution in a silver reductor... 

Although as already stated the use of metal amalgams, and in particular use of the Jones reductor or of the related silver reductor, is the best method of reducing solutions in preparation for titration with an oxidant, it may happen that for occasional use there is no Jones reductor available, and a simpler procedure will commend itself. In practical terms, the need is most likely to arise in connection with the determination of iron, for which the reduction of iron(III) to iron(II) may be necessary. 

Determination of uranium with cupferron Discussion. Cupferron does not react with uranium(VI), but uranium(IV) is quantitatively precipitated. These facts are utilised in the separation of iron, vanadium, titanium, and zirconium from uranium(VI). After precipitation of these elements in acid solution with cupferron, the uranium in the filtrate is reduced to uranium(IV) by means of a Jones reductor and then precipitated with cupferron (thus separating it from aluminium, chromium, manganese, zinc, and phosphate). Ignition of the uranium(IV) cupferron complex affords U308. 

Reductant equivalent weights of, 847 Reduction 409 by chromium(II) salts, 409 by hydrogen sulphide, 416 by Jones reductor (zinc amalgam), 410 by liquid amalgams, 412 by silver reductor, 414 by sulphurous acid, 416 by tin(II) chloride, 415 by titanium(II[), 410 by vanadium(II), 410 see also Iron(III), reduction of Reduction potentials 66 Reference electrodes potentials, (T) 554 Relative atomic masses (T) 819 Relative error 134 mean deviation, 134... 

Bajic and Jaselskis [153] described a spectrophotometric method for the determination of nitrate and nitrite in seawater. It included the reduction of nitrate and nitrite to hydroxylamine by the zinc amalgam reactor (Jones reductor) at pH 3.4 and reoxidation of the product with iron (III) in the presence of ferrozine. Interference by high levels of nitrite could be eliminated with azide treatment. Levels of nitrate of 0.1 mg/1 could be detected with a precision of 3% in the presence of large amounts of nitrite and chloride. 

Jones reductor -for iron compounds [IRON COMPOUNDS] (Vol 14)... 

The carbon monoxide and hydrogen in the producer gas are not completely converted in reducing iron oxide. Heating value plus sensible heat at 1520°F in the gas exiting from the reductor represent 54% of the input coal fuel value. Part of this energy,... 

Reductor columns have been prepared from zinc, silver, lead, cadmium, bismuth, antimony, nickel, copper, tin, and iron. 

A solution prepared by dissolving a 0.2256-g sample of electrolytic iron wire in acid was passed through a Jones reductor. The iron(Il) in the resulting solution required a 35.37-mL titration. Calculate the molar oxidant concentration if the titrant used was (a) Ce (product Ce +). 

A 0.7120-g specimen of iron ore was brought into solution and passed through a Jones reductor. Titration of the Fe(II) produced required 39.21 mL of 0.02086 M KMn04. Express the results of this analysis in terras of (a) percent Fe and (b) percent Fe203. 

Uranium. A sample containing ca. 2 millimols of uranium is fumed down with sulfuric acid in a 150-ml. beaker to remove nitrate. Then 20 ml. of 18 M sulfuric acid and 20 ml. of 85% phosphoric acid are added, and the solution is diluted with water to 75 to 80 ml. and cooled. This solution is passed over amalgamated zinc in a reductor at a rate of 30 ml./min. The reductor is washed successively with one 20-ml. portion of 3 Af sulfuric acid, three 40-ml. portions of 7.5% sulfuric acid, and one 40-ml. portion of water, the washings being added to the reduced solution. The resulting light bluish-green uranium (IV) solution is treated with 30 ml. of iron(III) chloride solution (100 g. of the 6-hydrate per liter) and allowed to stand for 5 to 10 min. or until it becomes distinctly yellow. Fifteen milliliters of 85% phosphoric acid and 8 drops of diphenyl-aminesulfonic acid indicator are added, and the solution is titrated immediately with 0.1 N potassium dichromate to a sharp purple end point. 

The checkers analyzed for molybdenum by dissolving the sample in 5% H2S04 and reducing to Mo(III) in a Jones reductor (30-mesh zinc amalgam). The reduced solution was received directly in acidic iron(III) sulfate solution and was titrated with a standard cerium(IV) solution with ferroin as the indicator. 

In aqueous solution many metal ions are reduced by sodium borohydride to borides [for example, Ni(II) and Co(II)], to the metal [for example, Ag(I)], or to a lower oxidation state [for example, Ce(IV) converted to Ce(III)]. Some of these reactions have found analytical application for example, analysis of iron, wherein NaBFL replaces SnCL or the Jones Reductor. 

Other reductor systems can be used, which will yield equally satisfactory results [25]. These can be the Jones, lead, cadmium, iron, nickel, or bismuth reactors, with the Jones reactor being chosen for use in the compendial assay method. Liquid mercury amalgams can also be used as redactors, being prepared with zinc, cadmium, bismuth, lead, or tin. While the liquid amalgams are easier to handle, and are more rapid than are column reactors, none of these is as simple as the aluminum foil reductor. 

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