Oxidation by chlorine

The methods described earlier for determining the total, free, or combined chlorine residual also are used in establishing the chlorine demand of a water supply. The chlorine demand is defined as the quantity of chlorine that must be added to a water supply to completely react with any substance that can be oxidized by chlorine while also maintaining the desired chlorine residual. It is determined by adding progressively greater amounts of chlorine to a set of samples drawn from the water supply and determining the total, free, or combined chlorine residual. 

Va.na.dlum(III) Oxide. Vanadium(III) oxide (vanadium sesquioxide, V2O2) is a black soHd, having the comndum (AI2O2) stmcture. It can be prepared by reduction of the pentoxide by hydrogen or carbon. Air oxidation proceeds slowly at ambient temperatures, but oxidation by chlorine at elevated temperatures to give VOCl and V20 is rapid. 

Dichlorine monoxide, which exists in very low equiUbrium concentrations in dilute HOCl solutions, is nevertheless a kineticaHy significant reactant. Eor example, although tetracyanonickelate(II) can be oxidized by chlorine in aqueous solution to /n j -Ni(III) (CN)4(H20)2 , the second-order rate constant at 25°C for oxidation with CI2O is 40 times greater than for CI2 and 2.6 x 10 greater than for HOCl (31). 

The only drawback of this dye is poor chlorine-fastness, which is considered to be due to the oxidation by chlorine to form a yellowish green a2ine... 

Interaction of EMT with chlorine and monochloramine has been studied. Electronic spectra of EMT and of its product of oxidation by chlorine and monochloramines have been obtained. X = 470 nm for EMT, 400 nm and... 

It is known that not all reactions proceed in the same manner on all adsorbent layers because the material in the layer may promote or retard the reaction. Thus, Ganshirt [209] was able to show that caffeine and codeine phosphate could be detected on aluminium oxide by chlorination and treatment with benzidine, but that there was no reaction with the same reagent on silica gel. Again the detection of amino acids and peptides by ninhydrin is more sensitive on pure cellulose than it is on layers containing fluorescence indicators [210]. The NBP reagent (. v.) cannot be employed on Nano-Sil-Ci8-100-UV2S4 plates because the whole of the plate background becomes colored. 

The distinction between the first member of the group and the two heavier members, which was seen to be so sharp in the early groups of transition metals, is much less obvious here. The only unsubstituted, discrete oxoanions of the heavier pair of metals are the tetrahedral [Ru 04] and [Ru 04]. This behaviour is akin to that of iron or, even more, to that of manganese, whereas in the osmium analogues the metal always increases its coordination number by the attachment of extra OH ions. If RUO4 is dissolved in cold dilute KOH, or aqueous K2RUO4 is oxidized by chlorine, virtually black crystals of K[Ru 04] ( permthenate ) are deposited. These are unstable unless dried and are reduced by water, especially if alkaline, to the orange... 

This reaction is called the breakpoint chlorination the combined chlorine level, which was rising as more chlorine was added, now drops suddenly. Free chlorine then rises without a corresponding rise in combined chlorine. This indicates that the pool pollution has been successfully oxidized by chlorine. 

Oxidation by chlorine to the arylimidosulfonyl chlorides is sometimes violent, and tert-butyl hypochlorite is a milder reagent. 

In the Falconbridge process, copper-containing nickel mattes produced by preliminary pyro-metallurgical processing of ore concentrates (see Figure 2) are oxidized by chlorine in reactions in which Cu11 is responsible for electron transfer to the metal. 

Although the BDS resin is very stable, as with all ion-exchange resins, it is susceptible to oxidation by chlorine. For this reason, any residual chlorine in the brine after vacuum dechlorination should be reduced prior to BDS treatment. This is typically done with sodium bisulphite. The small additional sulphate load that results can easily be handled by the BDS system. 

Table. Experimental on [1] and calculated values lg(k) for kinetic of propanthiol oxidation by chlorine dioxide...

Spectrophotometry (or colorimetry) has been used to measure chlorine dioxide in water using indicators that change colors when oxidized by chlorine dioxide. Spectrophotometric analyzers determine the concentration of chlorine dioxide by measuring the optical absorbance of the indicator in the sample solution. The absorbance is proportional to the concentration of the chlorine dioxide in water. Indicators used for this technique include jV,jV-diethyl-p-phenylenediamine, chlorophenol red, and methylene blue (APHA 1998 Fletcher and Hemming 1985 Quentel et al. 1994 Sweetin et al. 1996). For example, chlorophenol red selectively reacts with chlorine dioxide at pH 7 with a detection limit of 0.12 mg/L. The interferences from chlorine may be reduced by the addition of oxalic acid, sodium cyclamate, or thioacetamide (Sweetin et al. 1996). 

Bromine is obtained from natural brines, salt beds and seawater. The bromide salts extracted from these sources are oxidized by chlorine to yield bromine ... 

In Ketazine processes, hydrazine derivatives are obtained first. Ammonia is oxidized by chlorine or chloramines in the presence of aliphatic ketones. The products are hydrazones and isohydrazones. These are converted to ketazines with excess ketone. The ketazines or the intermediate hydrazine derivatives may be hydrolyzed to hydrazine after all the oxidizing reactants, such as CI2, NaOCl, or NH2CI are consumed. Unlike hydrazine, ketazines do not readily oxidize, and, therefore, the product yield is higher in these processes. 

Hydrogen sulfide enters natural waters from decay of organic matter (e.g., in swamps), bacterial reduction of sulfate ion, or underground sour natural gas deposits. It can be removed by aeration, anion exchange (Eq. 14.14), or oxidation by chlorine to elemental sulfur ... 

Add a potassium permanganate solution to one of an iron(II) salt acidified with sulphuric acid. What happens Write the equations of the reactions of an iron(II) salt with potassium permanganate and with potassium dichromate. Will an iron(ll) salt be oxidized by chlorine, bromine, and iodine water (see Appendix 1, Table 21) How do iron(II) salts react with hydrogen sulphide and ammonium sulphide ... 

Reaction with Other Halides. Bromide ion is oxidized by chlorine to bromine. This is the basic reaction in the production of bromine from seawater, brines, or bitterns. 

Properties.—The blue solution is unstable and decomposes slowly, with formation of sulphuric acid, sulphur dioxide and nitrogen dioxide. When shaken with air or submitted to oxidation by chlorine, nitric acid or hydrogen peroxide, conversion into nitrosulphonic acid is effected, brown fumes being liberated. Dilution -with water also destroys the coloured substance. If strongly cooled, the solution changes to an intense red, so that if a solution is too weak to possess a marked colour at the ordinary temperature, the presence of the purple acid can easily be detected by cooling in a mixture of acetone and solid carbon dioxide. 

During chlorination, destruction of the colouring matter and further decomposition of other substances accompanying the cellulose proceeds, all these substances being oxidized by chlorine or hypochlorite. 

In the formation of sodium chloride, sodium metal is oxidized by chlorine gas and chlorine gas is reduced 6y sodium metal. 

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