Chemical sulphur dioxide

Alternatively cellulose is produced from wood via wood pulp. A number of processes are used in which the overall effect is the removal of the bulk of the non-cellulosic matter. The most widely used are the sulphite process, which uses a solution of calcium bisulphite and sulphur dioxide, the soda process using sodium hydroxide and the sulphate process using a solution of sodium hydroxide and sodium sulphide. (The term sulphate process is used since sodium sulphate is the source of the sulphide.) For chemical purposes the sulphite process is most commonly used. As normally prepared these pulps contain about 88-90% alpha-cellulose but this may be increased by alkaline purification and bleaching. 

Transfer of an active chemical agent in an inherently safer form (e.g. sulphur dioxide as sodium metabisulphite, chlorine as sodium hypochlorite). Generation of an active agent in this manner clearly reduces the inventory in use. 

Impermeable timbers have a good resistance to polluted atmospheres where acid fumes rapidly attack steel. Wood has given excellent service in the buildings of chemical works and railway stations. Permeable wood species and sapwood can suffer defibration problems caused by the sulphur dioxide of industrial atmospheres. Tile battens are particularly vulnerable. The heartwood of Douglas fir, pitch pine, larch, Scots pine/European redwood and many tropical hardwoods give good service in these conditions. 

The UK Environment Agency deals with over 6000 oil pollution incidents each year. One estimate suggests that the chemical industry contributes to 50% of all air pollution with proportions approximating to sulphur dioxide (36%), carhon dioxide (28%), nitrogen oxides (18%), carbon monoxide (14%) and black smoke (10%). Motor spirit refining is responsible for ca 26% of emissions of volatile organic compounds to the atmosphere. In 1996 there were over 20 000 reports of water pollution incidents with 155 successful prosecutions. 

Substances Hazardous to Health, See also Toxic chemicals, 19, 138, 140 Substitution, 133 Sulphur, 30 Sulphur dioxide first aid, 280, 306 physical properties, 306 physiological properties, 69, 71, 304, 305 precautions, 305, 306 vapour pressure, 305 Suppression, 135 Surface area effects, 50, 199 Symbols for dangerous substances, 446, 452 Synthetic lubricants, 159 Synthetic resins, 172 Systemic poisons, 19, 77... 

Bunimovich, G. A., Matros, Yu. Sh., and Boreskov, G. K., Unsteady state performance of sulphur dioxide oxidation in production of sulfuric acid, in Frontiers in Chemical Reaction Engineering, Vol. 2 (Doraiswarmy, L. K., and R. A. Mashelkar, Eds.). Wiley Eastern, New Delhi, 1984. 

Sulphuric acid is an important industrial chemical. It has been said that the output of sulphuric acid is a measure of the wealth of a country, as it is used in the manufacture of fertilisers, detergents, pigments and fibres, amongst many other products. In the first stage of the process, sulphur is burned to produce sulphur dioxide. 

Acid rain is one of the worst manifestations of the damage we, as humans, inflict on our planet. Chemicals combine with elemental oxygen during the burning of fossil fuels, trees and rubbish to generate large amounts of acidic oxides such as nitrogen monoxide (NO), carbon dioxide (CO2) and sulphur dioxide (SO2). 

Chlorosulphonated polyethylene is obtained by reacting low density polythylene with chlorine in presence of sulphur dioxide using carbon tetrachloride as solvent. The product contains 30 per cent chlorine and 1.5 per cent sulphur. This is a sticky rubbery material and is soluble in chlorinated hydrocarbon solvents. It can be vulcanised by heating with metal oxides like litharge or magnesium oxide in presence of water. The cross-linked product is found to be resistant to chemical attack and is used in gaskets, hoses, etc. 

A plethora of chemical compounds for the determination of small amounts of water present in organic solids, pharmaceutical substances and organic solvents have been devised over a length of time. But unquestionably the most important of these is the one proposed by Karl Fischer (1935), which is considered to be relatively specific for water. It essentially makes use of the Karl Fischer reagent which is composed of iodine, sulphur dioxide, pyridine and methanol. 

Although, as described by Bjerle et alS13 liquid jet-type absorbers are also used, one relatively recent application of mass transfer in agitated tanks with chemical reaction is the absorption of pollutants from flue gases and, in particular, the scrubbing of sulphur dioxide by a slurry containing fine limestone particles. In this case, the concentration of sulphur dioxide is usually very low and the mechanism of the absorption is complicated due to the presence of solids in the liquid phase where the rate of solid dissolution may significantly affect the absorption rate. 

Inorganic chemistry is the study of the structure, relationships, and interactions of all the nonliving materials that make up the earth s crust, as well as the waters and the atmosphere. Thus, it includes the study of metals, such as iron, mercury, and lead of gases, such as oxygen, hydrogen, and sulphur dioxide of acids, such as sulphuric and hydrochloric of salts, such as sodium chloride (common salt) and potassium chloride, and so on—all the chemicals, in fact, that are not, or have not been, part of living tissue. 

The alchemists believed that a most minute proportion of the Stone projected upon considerable quantities of heated mercury, molten lead, or other "base" metal, would transmute practically the whole into silver or gold. This claim of the alchemists, that a most minute quantity of the Stone was sufficient to transmute considerable quantities of base" metal, has been the object of much ridicule. Certainly, some of the claims of the alchemists (understood literally) are out of all reason but on the other hand, the disproportion between the quantities of Stone and transmuted metal cannot be advanced as an a priori objection to the alchemists claims, inasmuch that a class of chemical reactions (called "catalytic") is known, in which the presence of a small quantity of some appropriate form of matter — the catalyst — brings about a chemical change in an indefinite quantity of some other form or forms thus, for example, cane-sugar in aqueous solution is converted into two other sugars by the action of small quantities of acid and sulphur-dioxide and oxygen, which will not combine under ordinary conditions, do so readily in the presence of a small quantity... 

So far, no reference has been made to the presence of more than one phase in the reactor. Many important chemicals are manufactured by processes in which gases react on the surface of solid catalysts. Examples include ammonia synthesis, the oxidation of sulphur dioxide to sulphur trioxide, the oxidation of naphthalene to phthalic anhydride and the manufacture of methanol from carbon monoxide and hydrogen. These reactions, and many others, are carried out in tubular reactors containing a fixed bed of catalyst which may be either a single deep bed or a number of parallel tubes packed with catalyst pellets. The latter arrangement is used, for exjimple, in the oxidation of ethene to oxiran (ethylene oxide)... 

Figure 5.20 — Reversible flow-through optical waveguide gas sensors using a reagent immobilized on the inner walls of the tube for the determination of moisture (water) (A) and sulphur dioxide (B). For details, see text. (Reproduced from [64] and [65] with permission of the American Chemical Society and Elsevier Science Publishers, respectively).

The oxidation of sulphur dioxide to trioxide is one of the oldest heterogeneous catalytic processes. The classic catalyst based on V2Os has therefore been the subject of numerous investigations which are amply reviewed by Weychert and Urbaneck [346]. These authors conclude that none of the 34 rate equations reported is applicable over a wide range of process conditions. Generally, these equations have the form of a power expression, in which the reverse reaction is taken into account within the limits imposed by chemical equilibrium, viz. 

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