Sulphur oxides

Sulphur oxide dichloride is a colourless liquid which fumes in moist air. It is hydrolysed by water to give a mixture of sulphurous and hydrochloric acids ... 

Sulphur oxide dichloride is used as a chlorinating agent in organic chemistry, for example in the preparation of acid chlorides ... 

A somewhat similar reaction is the power of sulphur oxide dichloride to remove water of crystallisation from hydrated chlorides, the hydroxyl groups of the water molecule reacting as do those in the acid molecules in the above reaction. 

In both reactions above, the oxide dichloride is refluxed with the acid or the hydrated chloride the sulphur dioxide and hydrogen chloride pass off and any unused sulphur oxide dichloride is distilled off in vacuo. 

Sulphur oxides G Sulphur dioxide Sulphur trioxide Coal distillation Combustion of coal and heavy fuel oil Detergents (sulphonation of alkyl benzenes) Electricity generation... 

Combustion processes are the most important source of air pollutants. Normal products of complete combustion of fossil fuel, e.g. coal, oil or natural gas, are carbon dioxide, water vapour and nitrogen. However, traces of sulphur and incomplete combustion result in emissions of carbon monoxide, sulphur oxides, oxides of nitrogen, unburned hydrocarbons and particulates. These are primary pollutants . Some may take part in reactions in the atmosphere producing secondary pollutants , e.g. photochemical smogs and acid mists. Escaping gas, or vapour, may... 

Sulphur oxides These (SO2 is the most frequently encountered oxide) are powerful stimulators of atmospheric corrosion, and for steel and particularly zinc the correlation between the level of SO2 pollution and corrosion rates is good However, in severe marine environments, notably in the case of zinc, the chloride contamination may have a higher correlation coefficient than SO2. 

Mechanism and sulphur oxidation Apart from its intrinsic interest the economic importance of acid corrosion and more lately interest in ore leaching, has stimulated considerable work on the oxidation of sulphur, Fe and Mn. It must be stressed that the Thiobacilli are obligate aerobes, i.e. that depend on molecular oxygen as a terminal electron acceptor. Possible reactions for the oxidation of sulphur are... 

Air contaminants Gases sulphur oxides, halogen compounds Mists aerosols, salt, alkalies Particulates sand, dust, grease... 

It has long been recognized that local environmental characteristics influence the rates of material corrosion. After two years of measurements at 39 sites in Europe and North America, significant relationships have been shown between corrosion rates of building materials and atmospheric pollutants( 5). While direction of exposure relative to weather and other factors such as frequency and duration of wetting significantly influence corrosion, Kucera (46) has shown that sulphur oxides are strongly correlated with deterioration of structural materials. 

Sulphur Oxides and Suspended Particulate Natter. Environmental Health Criteria Document No. 8, Geneva, Switzerland, 1979. 

Sulphur oxides G Sulphur dioxide Metal extraction and refining Coal distillation... 

The sulphite aftertreatment is particularly important with permonosulphuric acid treatment. Evidence for the underlying mechanism is available from analysis of sulphur oxidation products formed in the various processes (Table 10.34). It is evident from these results that the concentration of RSS()5 anionic groups necessary to change the hydration of the fibre surface is achieved by the reaction of bisulphite with cystine monoxide residues to give the required cysteine-S-sulphonate groups [311]. 

Table 10.34 Relative amounts of sulphur oxidation products formed during shrink-resist processing of wool [11,311]...

Red, brown and black iron oxides are prepared by first heating green iron(II) sulphate crystals to remove six of the molecules of water of crystallisation (leaving FeS04.H20) and then calcining the product to the desired form of iron(III) oxide with the evolution of sulphur oxides. 

Data from the EEA (2006c) reveal that air emissions from transport follow a slightly less expressed, but well comparable trend to entire emissions between 1990 and 2004. Table 19.2 shows the share for the transport sector of certain pollutants in the EU 40% to 50% of NO, and carbon monoxide (CO), 25% of non-methane volatile organic compounds (NMVOC) and just 1% of sulphur oxides (SO,). In developing countries, and here in particular in the big megacities, the share for transport of SO, heavy metal and particulate emissions (not listed here) will -because of the old vehicle fleets - be much higher. 

---