Zinc reductor

The silver reductor has a relatively low reduction potential (the Ag/AgCl electrode potential in 1M hydrochloric acid is 0.2245 volt), and consequently it is not able to effect many of the reductions which can be made with amalgamated zinc. The silver reductor is preferably used with hydrochloric acid solutions, and this is frequently an advantage. The various reductions which can be effected with the silver and the amalgamated zinc reductors are summarised in Table 10.11. ... 

The concentrates were subsequently analysed for arsenic using Varian-Techtron AAS atomic absorption spectrophotometer fitted with a Perkin-Elmer HGA 72 carbon furnace, linked to a zinc reductor column for the generation of arsine (Fig. 5.3). A continuous stream of argon was allowed to flow with the column connected into the inert gas line between the HGA 72 control unit and the inlet to the furnace. Calcium sulfate (10-20 mesh) was used as an adsorbent to prevent water vapour entering the carbon furnace. The carbon tube was of 10 mm id and had a single centrally located inlet hole. 

Maher [130] has described a procedure for the determination of total arsenic in sediments. Arsenic is converted into arsine using a zinc reductor column, as shown in Fig. 12.8. The evolved arsine is trapped in a potassium iodide-iodine solution and other arsenic determined spectrophotometrically as an arsenomolybdenum blue complex. The detection limit is 0.024pg and the coefficient of variation is 5.1% at the 0.1 pg level. The method is free from interferences by other elements at levels normally encountered in sediments. In this method the sediments were freeze-dried and ground (to less than 200pm) before analysis. 

The arsenic in each fraction was determined by reduction to the corresponding arsine in the zinc reductor column, decomposition of the... 

The zinc reductor, commonly known as the Jones ° reductor, generally is prepared from amalgamated zinc. The addition of mercury does not affect the standard potential of the Zn -Zn couple (—0.7628 V) as long as solid zinc is present. The rate of reduction, however, depends on the concentration of zinc at the surface of the amalgam. With relatively strong oxidants, such as Fe(III) and Ce(IV), which are reduced by mercury, a mercury content of 1 or even 5% may be used at high acid concentrations to control the rate of hydrogen evolution. With weaker oxidants the mercury content should be minimized so that the reduction reaction is not retarded. 

The silver reductor, often called the Walden reductor, is much more selective than zinc as a reducing agent. A hydrochloric acid solution is always used. The electrode potential varies with the concentration of chloride therefore the acid concentration is more critical than with the zinc reductor. From... 

The lead reductor (E° = —0.126 V) was proposed by Treadwell. If hydrochloric acid more concentrated than 2.5 M is used, lead sulfate films do not form even if highly concentrated sulfuric acid is present. The most important application of the lead reductor is in the reduction of U(VI) to U(IV). Its advantages over the zinc reductor lie mainly in its ability to reduce uranium to a definite oxidation state and in avoidance of certain interferences. 

The cadmium reductor has been used by Treadwell as a substitute for the zinc reductor. One application was the reduction of chlorate to chloride. Perchlorate was reduced to chloride only in the presence of a small amount of titanium ion as a catalyst. 

In the case of nitrate, the majority of applications for its determination are based on copperized-cad-mium or cadmium-coated zinc reductor columns, which are generally used for reducing nitrate to nitrite. After formation of color, specific reagents are added and nitrate is determined from the difference between the total nitrite and nitrate concentrations. 

Jones reductor A tube containing zinc amalgam. Used for reduction of solutions (e.g. 

REDUCTION WITH AMALGAMATED ZINC THE JONES REDUCTOR 10.138... 

Silver reductor hydrochloric acid solution Amalgamated zinc (Jones) reductor sulphuric acid solution... 

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 chem A device used to chemically reduce solutions, such as ferric salt solutions, consisting of a vertical tube containing granular zinc into which the solution is poured. jonz ri.dok-tor ... 

The reduction of aqueous chromium(III) solutions can be carried out electrolytically o chemically with zinc amalgam, zinc and acid or a Jones reductor.2,24 Electrolytic procedures ca be cumbersome, and with chemical reductants contamination with other products can occur Chromium metal and acid can be used to reduce chromium(III) salts, and this requires less c the metal than in the method described in Section 35.3.1.1.i. 

Jones reductor A column packed with zinc amalgam. An oxidized analyte is passed through to reduce the analyte, which is then titrated with an oxidizing agent. 

Prepare zinc amalgam for use as follows Add 20- to 30-mesh zinc to a 2% mercuric chloride solution, using about 100 mL of the solution for each 100 g of zinc. After about 10 min, decant the solution from the zinc, then wash the zinc with water by decantation. Transfer the zinc amalgam to the reductor tube, and wash the column with 100-mL portions of 2 N sulfuric acid until 100 mL of the washing does not decolorize 1 drop of 0.1 N potassium permanganate. 

It is alloyed with about 4% A1 and 0.02% Mg. The aluminum strengthens the zinc and also prevents the molten alloy from attacking the steel pressure casting dies. Zinc readily reacts with mercury or will displace mercury from a mercury(II) salt to form an amalgam that is usefril for reductions, as in the preparation of compounds of the lower oxidation states of transition metals and lanthanides (e.g. Cr , V , Eu°, dimeric Mo ) and in analytical chemistry (e.g. in the Jones reductor see Analytical Chemistry of the Transition Elements). 

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

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