Chlorine dioxide examples

Only chloric(III) acid, HCIO2, is definitely known to exist. It is formed as one of the products of the reaction of water with chlorine dioxide (see above). Its salts, for example NaClOj, are formed together with chlorates)V) by the action of chlorine dioxide on alkalis. Sodium chlorate(III) alone may be obtained by mixing aqueous solutions of sodium peroxide and chlorine dioxide ... 

Surface area can accelerate the decomposition of chlorine dioxide up to a point, but sufficient area appears to inhibit catalytic decomposition by adsorption of the intermediates. For example, the presence of fluffed wood pulp or glass wool is reported to stop the explosive decomposition of chlorine dioxide (27). 

Lactide/glycolide polymers have been investigated for delivery of agents in applications outside the pharmaceutical field. For example, the microbiocidal properties of chlorine dioxide disinfectants have been improved by formulating a long-acting chlorine dioxide system based on lactide/glycolide copolymers. Blends of microspheres based on 50 50 and 87 13 copolymers were developed to afford the release of chlorine dioxide over several months (114). 

Sodium hypochlorite could also be dangerous when hot, and alkaline chlorites also in this case however it is not guaranteed that the acid character of this example is sufficient to form chlorine dioxide. Caution is still required when handling these mixtures to which chlorates and perchlorates can be added. 

Chlorine dioxide has been evaluated as a replacement for chlorine [1630]. Gaseous chlorine as a biocide for industrial applications is declining because of safety and environmental and community impact considerations. Various alternatives have been explored, for example, bromo-chorodimethyl hydan-toin (BCDMH), nonoxidizing biocides, ozone, and chlorine dioxide. Chlorine dioxide offers some unique advantages because of its selectivity, effectiveness over a wide pH range, and speed of kill. Safety and cost considerations have restricted its use as a viable replacement. 

SPEGLs or EEGLs are available, IDLH levels provide alternative criteria. However, because IDLH levels were not developed to account for sensitive populations and because they were based on a maximum 30-min exposure period, the EPA suggests that the identification of an effect zone should be based on exposure levels of one-tenth the IDLH level. For example, the IDLH level for chlorine dioxide is 5 ppm. Effect zones resulting from the release of this gas are defined as any zone in which the concentration of chlorine dioxide is estimated to exceed 0.5 ppm. Of course, the approach is conservative and gives unrealistic results a more realistic approach is to use a constant-dose assumption for releases less than 30 min using the IDLH level. 

Initially all membranes were exposed to 3 ppm chlorine in buffer solutions at pH levels of 3.0, 5.8, and 8.6 for three weeks. Both cellulose acetate type membranes C-2 and V-1 were unaffected by chlorine under these conditions. Continued exposure at higher chlorine levels did not alter baseline membrane performance. For example, membrane C-2 exposed to 125 ppm chlorine for 10 days at pH 3 continued to perform at baseline levels. In subsequent work, cellulose acetate membranes were also found to be unresponsive to bromine, iodine, and chlorine dioxide. It can be generally concluded that cellulose acetate type membranes are halogen resistant. 

In the textile industry, chlorine dioxide is used as a bleaching agent and produces high-quality textile fibers with additional qualities. For example, shrinkproof wool owes its qualities to the reaction of chlorine dioxide with the cross-linking sulfur atoms of the wool. 

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). 

G. S. Serullas treated potassium chlorate with an excess of hydrofluosilicic acid the clear liquid was decanted from the sparingly soluble potassium fluosilicate, the soln. evaporated below 30°, and filtered through glass powder J. J. Berzelius evaporated the acid liquid mixed with finely divided silica below 30° in air, or over cone, sulphuric acid and potassium hydroxide in vacuo. The excess of hydrofluoric acid was volatilized as silicon fluoride, and the clear liquid was then filtered from the excess of silica. R. Bottger treated sodium chlorate with oxalic acid whereby sparingly soluble sodium oxalate was formed J. L. Wheeler, and T. B. Munroe treated sodium chlorate with hydrofluosilicic acid and M. Brandau treated potassium chlorate with aluminium sulphate and sulphuric acid and precipitated the alum so formed with alcohol. Chloric acid is formed in many reactions with hypochlorous and chlorous acid for example, it is formed when an aq. soln. of chlorine or hypochlorous or chlorous acid decomposes in light. It is also formed when an aq. soln. of chlorine dioxide stands in darkness or in light. A mixture of alkali chlorate and chlorite is formed when an aq. soln. of an alkali hydroxide is treated with chlorine dioxide. 

For certain cooling water applications, chlorine dioxide may be more suitable than chlorine for example, where the system is subject to heavy... 

The best opportunities for predicting redox transformations come from engineered systems where a known oxidant is added to achieve contaminant remediation. Well-documented examples include the use of ozone (Example 2.2.1.1) and chlorine dioxide (e.g., 41, 42) in... 

From these equations it is evident that 1 mole of chlorine has the same oxidation power as one gram-ion of CIO- (i. e. one mole of NaCIO or half a mole of Ca(C10)2), half a inole of NaC102. or finally, two fifths of a mole of chlorine dioxide. For example, one gram-molecule of pure calcium hypochlorite of 142.99 grams in weight has the same bleaching power as two moles of chlorine weighing 141.84 g. The content of active chlorine in this substance thus equals 141.84/142.99 = 99.19 per cent. 

Mixed Oxides.—In some cases so-called mixed acidic oxides are known which combine with water, producing a mixture of two acids nitrogen tetroxide is an example of this class, as also is chlorine dioxide—... 

In this reaction five oxidation equivalents are released. For example, 1 M Cl02 solution contains 5 x 35.5 = 177.5 g/liter of active chlorine. In alkaline media, chlorine dioxide is reduced to chlorite involving a change of only one oxidation equivalent. 

The oxidation pathways of chlorine dioxide under actual conditions are complex because a number of species including chlorine, hypochlorous, chlorous, and chloric acids are formed as intermediates. A rapid conversion of chlorine dioxide to chloride and chlorite (chlorous acid, pK 2.0) may first take place, followed then by a slow phase during which mainly the chlorite reacts with the pulp components. However, continuous generation of chlorine dioxide during bleaching takes place, for example, by the reaction between chlorite and chlorine (or hypochlorous acid) ... 

Fig. 8-10. Example of the reactions of a guaiacyl unit with chlorine dioxide and chlorine (Hardell and Lindgren, 1975).

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