Production of Chlorine - Case Study Example

Raw materials 1.0 Sources and properties of raw materials (feedstock): 1.1 Rock Salt, NaCl (halite) Rock salt is a mineral also known as halite. The mineral is mined for various uses including for human consumption as table salt. 1.1.2 Physical and chemical properties Rock salt has various physical and chemical properties. The mineral has the chemical formula, NaCl, and is also referred to as sodium chloride. Its normally white or colourless and forms small transparent crystals. The mineral also occurs in red, orange, yellow, pink, blue, green, gray, and violet due to impurities. It has no odour, but has a distinctive taste. It is easily soluble in water (35.9 g/100 mL), but almost insoluble in many other liquids including ethanol. Its melting point is 801 °C, while its boiling point is 1465 °C (1738 K). It’s brittle and its fracture is conchoidal. The equally charged sodium ions and chloride ions make it an ionic compound. When dissolved in water it conducts electricity. Electrical current can be used to decompose it into chlorine and sodium. 1.1.3 Sources Rock salt occurs in extensive stretch of sedimentary evaporite rocks that are the result of drying enclosed lakes, seas and playas. It forms when saline water evaporates in basins that are somewhat enclosed. This mineral is very prevalent worldwide, and occurs in underground deposits - more so in non-arid areas - and as a solution in seas or oceans as well as in several inland lakes of the arid areas. The United States is the largest producer of rock salt, with vast deposits of the mineral being in Michigan, Kansas, Ohio, Louisiana, New York, New Mexico, and Texas (Singh 2004. p.138). In Canada, which is also a key producer, has rock salt mines in Nova Scotia, Ontario, and Saskatchewan. In these two region, the main producers are Michigan, Ohio, and Ontario, which in 1987 produced 8.7 million tonnes, accounting for about 35 percent of the total production in both Canada and U.S. (Schaetzl 2004; United States Geological Survey 2008). In 2007, United produced an estimated amount of 45.4 million metric tonnes, compared to the worlds production of 257 million tonnes. The other major producers and sources of rock salt in the world include China, India, Germany, Australia, Mexico, Brazil, France, and the United Kingdom (United States Geological Survey 2008). Salt domes, which contain halite among other minerals, are common along the Louisiana and Texas Gulf coasts. These domes are also found in Spain, Germany, Romania, Iran, and Netherlands. In the arid parts of Iran salt glaciers are common in high elevation where they flow downhill, thus behaving like a rheid. The atypical purple coloured fibrous vein-filling rock salt exists in France and some other few regions. Halite flowers are found in some arid caves in Nullarbor Plain of Australia, and in the Quincy copper mines within Hancock city of New York. Other sources of rock salt worth noting are Chile, Egypt, Iran, Italy, Netherlands, Poland, Romania, Russia, Spain, Turkey, and Ukraine. 1.1.4 Market trends The production of rock salt has been increasing steadily with its increase in demand at the world market. The production in the United Kingdom has often reflected its market demand. In 1900, the United Kingdom consumed almost all its production. While the world production averaged about 12.2 million tonnes and world annual consumption in the first half of 1900 remained below 50 million tonnes, in the United Kingdom consumption was less than 6 million tonnes. There was rapid increase, however, in the mid twentieth century of the world consumption that echoed the global production of about 109 million tonnes in 1965 and 210 million in 1999 (United States Geological Survey 2008), although in the United Kingdom the production and consumption remained somewhat steady at about 5 to 6 million tonnes per year. This capacity remained stable throughout to the 21st century (Brown et al. 2009, p.92). The prices of rock salt have also been experiencing an upward trend as years progress. The price for one metric tonne of sodium chloride (or rock salt) stood at US$2.62 in 1900. This has risen to about US$33.40 in 2007. Historical prices of rock salt have shown consistent increases with each year, with some instances of price drop that are recovered in the following year. For instance, price of rock salt dropped by 4.3% to 19.80 per metric tonne in 1988, but regained its price to reach US$22 per metric tonne. While the price drop in 1991, 1995, 1997, 1998 have been in terms of cents (of the US dollar), the price increases have mostly been more than US$1. However, in 2000 the price of rock salt decreased by US$1, while between 2005 and 2006 price of rock salt increased by US$3.04. Since 2000 the prices of rock salt have been on an upward trend, reaching US$33.40 in 2007 (United States Geological Survey 2008). In 2008, the United States consumed salt in the proportion of 38% for rock salt, 44% for brine, 10% for vacuum pan, and 8% for solar salt. Out of the total rock salt production, 40 percent was used in the chemical industry, while 90% of the rock salt used in feedstock was brine. The caustic soda and chlorine industry have remained as the major consumer of rock salt in the United States. 1.1.5 Future Prediction The United Kingdom’s reserves for rock salt are extensive. The availability of rock salt, is therefore, sustainable to meet the future demands in UK. Its application to production of chlorine is, however, threatened due to the global trend in minimizing the use of chlorine. 1.2 Sodium Hydroxide, NaOH (caustic soda) 1.2.2 Physical and chemical properties Sodium Hydroxide has the molecular formula, NaOH. It is normally a brittle, translucent white crystalline solid. It deliquesces when exposed to air, and resolidifies as a result of forming sodium carbonate upon absorption of carbon dioxide. Caustic soda is highly soluble in water. Sodium hydroxide releases heat when its concentrated solution is diluted, or when its solid form is dissolved in water. Its aqueous solutions are very alkaline, and it forms sodium salts in neutralization reactions. It reacts with certain metals and metal oxides to form complex anions and hydrogen. It also reacts with gases like sulphur dioxide and carbon dioxide that form weak acids. 1.2.3 Sources Sodium hydroxide is co-produced with other products such as chlorine and soda ash. It is manufactured from rock salt in the same process that produce chlorine. The United States is the largest producer of caustic soda, with its production base in Wyoing and California(States Geological Survey 1998, p.156). There are several other sources of caustic soda in the world with Botswana, Kenya, Mexico, Turkey, and Uganda constituting some of the major producers. 1.2.4 Market trend (Prices) The demand for sodium hydroxide in the United Kingdom has risen since the twentieth century but recent data indicates declines in consumption. In 2001, the global demand was 46 million tonnes, while in the United Kingdom it was less than 5 million metric tonnes (Society for Mining, Metallurgy, and Exploration 2006). In between 1998 and 2002, there was a downward trend in demand for caustic soda globally including in the United Kingdom (Society for Mining, Metallurgy, and Exploration 2006). 1.2.5 Future Prediction Sodium hydroxide is expected to be available in the near future, and as long as chlorine and soda ash are still in production. Its availability is, however, threatened by the attempts to phase out chlorine production due to environmental concerns. The demand for sodium hydroxide is expected to grow in the following years when the world economy becomes stable. 1.3 Hydrogen chloride (HCl) Liquid 1.3.2 Physical and chemical properties Hydrogen chloride is a gas at standard temperature and pressure. Its between colourless and pale yellow in colour, and has a pungent smell. Its molecular weight is 36.5 daltons, boiling point is 760mm Hg (-121°F), density is 1.3, and solubility in water is 67% at 20°C (68°F). It is also soluble in alcohol, ether and benzene. It forms dense vapours when exposed to air, and is extremely corrosive to almost all metals. The gas also reacts with amines, alkalis, and hydroxides. 1.3.3 Sources Hydrogen chloride is obtained as a by-product in industrial processes that involve chlorination of organic compounds (Assembly of Life Sciences 1976, p.17). Thus, it is produced through the manufacture of chlorinated benzenes, vinyl chloride, benzenes toluenes, carbon tetrachloride, fluorocarbons, among other organic compounds. In fact, hydrogen chloride is a by product of any production process that involves chlorine in substitution reactions such that chlorine atom is replaced by hydrogen atom in a chemical compound. United States is a key source of hydrogen chloride. 1.3.4 Market trends Most of the industrial-produced hydrogen chloride is used in the production of hydrochloric acid (SRI International 2001). The demand for hydrochloric acid is, therefore, translates into demand for the hydrogen chloride gas. Between 2000 and 2005, the demand for hydrogen chloride has been characterised by an upward trend. In 2000, for instance, the demand for the commodity was about 3. 375 million short tonnes, but that increased to about 2.530 million short tonnes by 2005 (www.the-innovation-group.com). Furthermore, the historical annual growth in demand for the hydrogen chloride has been 1.5% (www.the-innovation-group.com). The prices of hydrogen chloride have varied extensively with time and location. Between 1996 and 2001, the prices stood at $138 for every short tonne, but it fluctuated to about $72 in 2005 (www.the-innovation-group.com). Recently, the prices for hydrogen chloride have been rising, a factor that can be attributed to the rising demand of hydrochloric acid and the priority of chlorine use to other options (China Chemical Reporter 1996). 1.3.4 Future predictions The availability of hydrogen chloride is largely dependent on the production of chlorine since it is produced as a co-product. In this respect, the production of hydrogen chloride is expected to be stable without much growth in demand for the commodity in the near future. Therefore, there is no expectation of shortage of hydrogen chloride. 1.4 Sodium Sulfite (NaHSO3) 1.4.2 Physical and chemical properties Sodium Sulfite is a white powder or crystals with faint smell of sulphur dioxide (FNP 1999). It is easily soluble in water, but moderately soluble in ethanol. It has a relative density of 2.63. It reacts with weak acids that decompose it into sulphur dioxide. An aqueous solution saturated with sodium sulphite has a pH of about 9. When exposed to air, sodium sulphite is oxidized and becomes sodium sulphate. 1.4.3 Sources Sodium sulphite is manufactured in several countries. The commercial sodium sulphite is manufactured from sodium carbonate, caustic soda or sulphur dioxide. This commodity is often coproduced with soda ash and caustic soda. United States is a key producer of sodium sulphite, which is manufactured mostly in soda ash plants. In the United States, it is produced in Texas’s Port Neches and Pasadena, North Claymont, Petrolia borough of Pennsylvania, Tacoma in Washington, Greener in Wyoming, Baton Rouge city of Lousiana, Tacoma area of Wyoming, and Tuscaloosa of Alaska California. Other main sources are in Canada, China and Europe (FNP 1999; http://www.the-innovation-group.com). 1.4.4 Market trend The current world demand for Sodium sulphite has increased since the 1990s. In 1999, the demand was about 110,000 short tonnes, that increased to 112,000 short tonnes. At the moment demands is still high, although the economic downturn has affected its consumption (http://www.the-innovation-group.com). Between 1995 and 2000, the price for sodium sulfite were at a high of $37 per centum weight, but dropped to about $27 per centum weight in the following years including 2004 (United States Geological Survey 2009; McKetta 1995). 1.4.5 Future Prediction The availability of sodium sulphite is largely dependent on production of chlorine. The pulping industry consumes more than half of sodium sulphite, and expected to spur growth of the sodium sulphite production (McKetta 1995; http://www.the-innovation-group.com). Nonetheless, the commodity has often been produced in excess of its requirement in the market (http://www.the-innovation-group.com), and growth in the near future in not expected especially with the economic downturn, Nonetheless, in the longer term, a growth of 1.1% is expected (McKetta, JJ 1995). There are no shortage of sodium sulphite expected in the near future, although the efforts to phase out chlorine threaten its availability. 1.5 Sodium Carbonate, Na2CO3 (soda ash) 1.5.2 Physical and chemical properties Sodium carbonate is a grey-white odourless powder at standard temperatures. It is soluble in water (about 22 g/100 ml at 20 °C), but insoluble in alcohol and ethanol. It is also hygroscopic such that it absorbs molecules of water spontaneously when exposed in the open air, and forms hydrates. Its melting point is 851°C, while its density is 2.53g/cm3. It tastes is alkaline, while its pH is basic. It is characterised by effervescences when put in a weak acidic solution, where it forms bubbles on decomposition. 1.5.3 Sources Sodium carbonate is obtained naturally from trona and brines rich in sodium carbonate, more so from in evaporite mineral deposit in the arid areas. It is synthetically produced from salt or sodium chloride. However, synthetic production is expensive and more harmful to the environment (States Geological Survey 1998, p.157). United States is the largest source of sodium carbonate with its main production being in Wyoming; it is also produced in California. The annual capacity of producers in the U.S. averages about 12 million tonnes (States Geological Survey 1998, p.156). There exists about 62 sources of sodium carbonate in the world. Besides the U.S. others main deposits and producers include Botswana, Kenya, Mexico, Turkey, Uganda. Egypt has been a source of sodium carbonate since ancient days (Dawson 1962). It is also found in the unique Ol Doinyo Lengai volcano in Tanganyika, as well as in the Kola peninsula. 1.5.4 Market trend The annual production of sodium carbonate in the United Kingdom is about one million tonnes (Lister 2009). There has been an upward trend in the prices of sodium carbonate, while the consumption has been decreasing in the recent past. The economic downturn, increasing production and transportation costs, which are influenced by the global consumption of energy have all contributed to this trend. The global consumption of soda ash was 46 million tonnes in 2008. The prices for soda ash in the United Kingdom have also been increasing. In 2004, the prices ranged between US$105 and US$130 per tonne and increased rapidly to an average of between US$260 and US$285 by 2008 (United States Geological Survey 2009, p.150). The 2009 data show lesser demand compared to 2008, while prices are still high (McKetta 1995; United States Geological Survey 2009, p.1). 1.5.5 Future Prediction There is an extensive deposits of limestone and trona in the United Kingdom that are used in the production of sodium carbonate. While these deposits are huge, their exploitation is high and their rate of depletion is high. However, there is no expectation of shortage of sodium carbonate in the United Kingdom in the near future even as the world demand is expected to grow at a rate of 2% (United States Geological Survey 2009, p.151). 1.6 Barium Carbonate, BaCO3 (Whitherite) 1.6.2 Physical and chemical properties Barium Carbonate is an odourless white powder or pellets at standard temperature and pressure. It solubility in water is about 0.02g/l at 20°C or 68°F, it has a relative density of 4.3, and its pH range between 7 and 8 at 20°C. It decomposes at temperature above 1400°C, but it is stable and standard conditions. It reacts with several acids to form barium salts that are soluble in water. 1.6.3 Sources Barium Carbonate is commercially obtained from reactions with barium sulfide or carbon dioxide, especially as a co-product in the manufacture of soda ash (Pradyot 2002, p.856). China and United States are the main source of Sodium carbonate. There more than forty producers of sodium carbonate in China, with it two phases of production in 2003 accounting for 50% and 70% of the world total (China Chemical Reporter 2004). Others sources are India, Canada, Europe, and some part of Africa. 1.6.4 Market trend The world demand and prices for barium carbonate have experienced a downward trend in many instances; this has been reflected in the United Kingdom. Between 1975 and 1985, there was decline in production and consumption of barium carbonate, mainly due to adoption of a different technology in purification of brine. Moreover, in 1998, the price of one tonne of barium carbonate was US$209 from its earlier price of US$228, which is about a 8.4% drop (China Chemical Reporter 1998). Barium Carbonate is the second most important barium product from barite in the United Kingdom. In 1989, its use was in the glass industry (30%), brick and clay (30%), manufacture of barium chemicals (20%), and in manufacture of barium ferrite (5%). 1.6.5 Future Prediction The availability of barium carbonate is largely dependent on the industrial production of soda ash. With the production of soda ash expected to grow, barium carbonate is expected to be sufficiently available for several years in the United Kingdom. Its demand is expected to increase in the long-term (Zogbi 2002), and with the economic downturn and increasing economic concern for chlorine production – a co-product of soda ash, its availability is likely to be threatened. Products 2.0 Uses and Application of chlorine (Cl2) gas Chlorine has many uses and applications. Its is used in the production of a number of both consumer and industrial products (Heaton 1996) such as plastics, textiles, metal degreasing and dry cleaning solvents, pharmaceuticals and agrochemicals products, household cleaning agents, dyestuffs, insecticides, etcetera. This chemical is also useful in purification of water – as applied in water treatment plants - and as a component in bleaches and disinfectants. Chlorine is a more effective disinfectant compared to bromine and iodine, for instance in killing the Escherichia coli bacteria (Koski, Stuart & Ortenzio 1966). It is often used as a hypochlorous acid in killing microbes such as bacteria in swimming pools and water supplies (Hammond 2000). It is a biocide. In its elemental form, chlorine is also used widely in both inorganic and organic chemistry in oxidizing and substitution processes. It is involved in substitution reactions with salts of lower halogens such as bromide and iodide, and oxidizes the halides into their elemental form. It is also involved in free radical substitution reactions with organic compounds containing hydrogen. This has been useful in the industrial production of substances such as chloroform, methyl chloride, carbon tetrachloride, and methylene chloride out of methane; tetrachloroethylene and trichloroethylene out of 1,2-dichloroethane; and allyl chloride out of propylene. Besides that, compounds of chlorine are utilized as intermediaries during the production of several products of commercial importance that are free from chlorine such as silicones, polycarbonates, propylene oxide, carboxymethyl cellulose, and polytetrafluoroethylene. Chlorine has also been used as a poisonous gas in wars among other uses. The gas reacts with water within the lung’s mucosa resulting into hydrochloric acid, which can be irritating and lethal. Moreover, chlorine is highly useful in manufacture several organic compounds of chlorine, including vinyl chloride and 1,2-dichloroethane that are intermediates in polyvinyl chloride (PVC) production. It is also used in producing useful organochlorines such as vinylidene chloride, perchloroethylene, chlorobenzene, epichlorohydrin, trichlorobenzenes, and dichlorobenzenes. It is also used in extraction of bromine and manufacture of chlorates. 2.1 A brief history of chlorine The chlorine gas was first discovered in 1774 by a Swedish chemist known as Karl Wilhelm Scheele in his laboratory experiment. He reacted hydrochloric acid (HCL) - then referred to as muriatic acid - and manganese dioxide (MnO2) and obtained a gas product among others that he named “dephlogisticated muriatic acid air” (Watt 2001, p.7). He categorized the substance as an oxide, but this would later be changed in 1810 by Humprey Davy who named it chlorine and classified it as an element (Davy 1811; Mellor 1912, p.233). The term was derived from the Greek word chlōros, that means green-yellow (Davy 1811). Scheele noticed many of its properties such as its bleaching outcome on litmus, its toxicity, its yellow greenish colour, and the aqua regia smell (Watt 2001, p.8). Joseph L. Gay-Lussac and Louis-Jacques had attempted in 1809 to decompose the substance (chlorine) without success and concluded faintly that it was an element Lussac & Thenard 1809). In 1811, Johann Salomo Christoph Schweigger classified chlorine as a halogen, a term that means salt producer. In 1823, and for the first time in history, Michael Faraday condensed chlorine into liquid (Clements 2005, p. ; Sebastian, 2001, p.). 2.2 Characteristics of chlorine Chlorine exists as a diatomic molecule (Cl2) of chlorine atoms at the standard pressure and temperature. It is light yellow-green in colour, with a distinctive intense smell. The chlorine molecule is extremely reactive due to the weak bond between its atoms, and readily reacts with almost every element. The element is part of the halogen group, which is the most reactive in the periodic table. Chlorine is less reactive than fluorine. Chlorines react with metals to form salts known as halides. It forms compounds with krypton, nitrogen, oxygen, and xenon, although not occur directly (Windholz, Budavari, Stroumtsos & Fertig 1976). The gas, in its pure form, supports combustion of some organic compounds like hydrocarbons; nonetheless, the carbon part tends not to burn completely and remains as soot (Hammond 2000). 2.3 Demand for chlorine There is demand for chlorine all over the world. The global consumption of chlorines was 34.5 million tonnes in 1987, which represents about 85% utilization of the total amount of chlorine produced globally (Curlin, Bommaraju & Hanson). The highest demand for chlorine is in North America, with Western Europe, Eastern Europe, Japan, Asia, and Latin America constituting subsequent demands. Basing on the 1987 data, the utilization of chlorine in both North America and the Western Europe constitute about 39% of the world demand. The highest demand for chlorine comes from industrial use, and in particular, in the manufacture of vinyl chloride monomer, which represents about 26% of all chlorines uses. The next demand of chlorine is for manufacture of pulp and paper, more so, in bleaching the kraft pulp; this is about 13% of chlorine utilization. Other key demands for chlorine are in production of ethylene dichloride, propylene oxide, chlorinated solvents, epichlorohydrin, hypochlorites, and in treatment of water. 2.4 Chlorine market observation - Price and Market trends In 1987, the main applications of chlorine was in production of vinyl chloride polymer, pulp and paper, propylene oxide, and in water treatment. During this period the Western Europe, with the United Kingdom taking the largest share, was the second largest consumer of chlorine at about 28.7% of the world consumption (Curlin, Bommaraju & Hanson). The composition of chlorine use has remained somewhat stable. The organic chemical and PVC industry still remains the main market for chlorine constituting about 76%. The average growth in the use of chlorine in epichlorohydrin and propylene oxide industry has averaged between 1.5% and 2% in the 1990s. This consumption, together with that in phospehene industry has recently experienced growth. However, use of chlorine in the pulp and paper industry has been on the decline since the 1990s. In 1990, about 949,218 tonnes of chlorine were consumed in the United Kingdom. This is out of the 940,305 tonnes produced internally and the 12,728 tonnes imported; its chlorine export was only 3815 tonnes (McLaren, et al. 1998, p.348). Consumption in 1992 was approximately 555,000 tonnes (UNECE 1995, McLaren, et. al 1998, p.348). In general, chlorine use in Western Europe has recently been on the decline, probably because of legislations seeking to discourage its use as well as due to concern on it effects on the environment. The use of 1,1,1-trichloroethane has been phased out in these regions because of its apparent damaging effect to the ozone layer and the environment. Chlorine use in the pulp and paper industry in the 1990 was 5% of the total demand in Western Europe, but this figure has recently decreased (Stringer & Johnston 2001, p.115). In fact, presently this sector together with water treatment accounts for only 2% of the total production of chlorine in Western Europe. Similarly, this period saw a decline in use of the elemental chlorine from about 20% to about 13% of the entire U.S. chlorine market. Chlorine is almost not used in the Scandinavian nations. Stringer and Johnston (2001, p.115) observes that chlorine is no longer in use in Sweden. Several kraft pulp milling company have abandoned the utilization of the elemental chlorine; at least 50 pulp mills worldwide don’t use the elemental chlorine, while about 10 mill don’t use chlorine at all (Stringer & Johnston 2001, p.115). The trends in chlorine use have been characterised by substitution of the elemental chlorine with, for instance, chlorine dioxide. The composition of demand for chlorine has remained somewhat steady. The highest demand globally comes from the PCV and polyurethane industry, which today stands at 55%. America still remains a large consumer of chlorine, with consumption in the developing countries growing. Between 2004 and 2008, for instance, China has experienced a growth of 50% in chlorine consumption (Linak, Schlag & Yokose 2008). The chlorine industry has been characterised by a cyclical trend in prices, such that there periods of high margins that follow low profitability. Between about mid 2000 and 2003, the industry was experiencing low margins with high prices, a situation that was worsened by increase in gas prices (Linak, Schlag & Yokose 2008). Prices for chlorine rose further in 2004, and although there was increase in profits, the high costs of energy offset the profitability. The prices of chlorine and products have remained extremely high throughout in 2006 through to 2008 in both the United Kingdom and Europe. 2.5 Future predictions It is expected that chlorine will be less available in the future. Chlorine is environmentally unfriendly (Hammond 2000 ; Koski, Stuart Ortenzio 1966), and there has been concerted efforts to eliminate the use of chlorine by 2050, with the expectation that 25 percent progress will be made by 2010 (McLaren, et. al 1998, p.348). The Commission of the European Communities has noted that there has been increased regulation of chlorine use which will affect future production of chlorine (1990, p. 76). However, in the near future, consumption of chlorine is expected to only increase moderately as there is little expectation on new capacity in the United Kingdom (Linak, Schlag & Yokose 2008). It is also worth to note that there is large reserve of raw materials that produce chlorine, and therefore, this commodity is likely to available for several years. Reference List American Chemical Society 1918, Journal of the American Chemical Society, Vol. 40. Pp.1546-1555 American Chemical Society. Assembly of Life Sciences (U.S.) 1976, Chlorine and hydrogen chloride, National Academy of Sciences, United States. Assembly of Life Sciences 1976, Chlorine and hydrogen chloride, National Academy of Sciences, United States. Brown, TJ, Hetherington, LE, Hannis, SD, Bide, T, Benham, AJ, Idoine, NE, Lusty, PAJ British Geological Survey 2009, World mineral production 2003 – 2007, Halstan & Co Ltd, United Kingdom. China Chemical Reporter 1996, Rising Price of Hydrochloric Acid, China Chemical Reporter, China. China Chemical Reporter 1998, Market Price of Barium Carbonate Sliding Down, China Chemical Reporter, China. China Chemical Reporter 2004, Present status and development trend of the barium carbonate and strontium carbonate market, China Chemical Reporter, China. Clements, G 2005, The Picture History of Great Inventors, frances lincoln ltd, London. Commission of the European Communities 1990, Panorama of EC industry 1990: describing over 165 sectors of the European Community's industry, including both manufacturing and services, Office for Official Publications of the European Communities. Curlin, L C, Bommaraju, T V, Hanson, CB, Chlorine and sodium hydroxide, Vol. 1 Davy, H 1811, "On a Combination of Oxymuriatic Gas and Oxygene Gas". Philosophical Transactions of the Royal Society. Vol. 101. Pp. 155- 62, . Dawson, JB 1962, "Sodium carbonate lavas from Oldoinyo Lengai, Tanganyika". Nature. Vol. 195. FNP 1999, Sodium sulfite, November 9, 2009, . Geological Survey of Great Britain & Robert Hunt 1867, Mineral statistics of the United Kingdom of Great Britain and Ireland, H.M.S.O, United Kingdom. Hammond, C R 2000, The Elements, in Handbook of Chemistry and Physics. 81st edn. CRC press, Australia. Heaton, C A 1996, An Introduction to industrial chemistry. 3rd edn. Springer, Australia. Hydrochloric Acid, November 14, 2009, Koski T A, Stuart L S, Ortenzio L F 1966, "Comparison of chlorine, bromine, iodine as disinfectants for swimming pool water". Applied Microbiology. Vol. 14. No. 2. Pp. 276-279. Kroschwitz, Jacqueline. 1991. Kirk-Othmer Encyclopedia of Chemical Technology, 4th Ed. New York: John Wiley & Sons. Linak E, Schlag, S & Yokose, K 2008, Chlorine/Sodium Hydroxide, November 5, 2009, . Lussac, J L G & Thenard, L J 1809, "On the nature and the properties of muriatic acid and of oxygenated muriatic acid", Mémoires de Physique et de Chimie, de la Société d'Arcueil. No. 2, Pp. 339-358. November 5, 2007, . Mansfield, C & Depro, BM 2000, Economic analysis of air pollution regulations: chlorine industry, Final Report, U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Air Quality Strategies and Standards Division, Research Triangle Park, NC. McLaren, D, Bullock, S, Yousuf, N, Friends of the Earth 1998, Tomorrow's world: Britain's share in a sustainable future, Earthscan, Mellor, J W & Parkes, G D 1967, Mellor's modern inorganic chemistry, 6th edn. Longmans, London. Mellor, J W 1912, Modern inorganic chemistry, Longmans, London. Pradyot P 2002. Handbook of Inorganic Chemicals. McGraw-Hill, New York. Schaetzl, R Rock salt mining, November 6, 2009, Sebastian, A 2001, A dictionary of the history of science, Informa Health Care, United States. Silliman, B, Dana, E S, Dana, J D 1833, The American journal of science and arts, S. Converse. Vol. 23. Pp. 129-133. Singh, T 2004, New horizons in tourism: strange experiences and stranger practices, CABI Publishing, United Kingdom. Society for Mining, Metallurgy, and Exploration 2006, Industrial minerals & rocks: commodities, markets, and uses, Society for Mining, Metallurgy, and Exploration, United States. Sodium Sulfite , November 9, 2009, . SRI International 2001, "Hydrochloric Acid". Chemicals Economics Handbook. SRI International. pp. 733.4000A - 733.3003F. Stringer, R & Johnston, P 2001, Chlorine and the environment: an overview of the chlorine industry, Springer, Australia. Susan R. Feldman. Sodium chloride. Kirk-Othmer Encyclopedia of Chemical Technology. John Wiley & Sons, Inc. Published online, 2005 doi:10.1002/0471238961.1915040902051820.a01.pub2 U.S. Environmental Protection Agency 2000, Barium carbonate listing background document for the inorganic chemical listing determination UNECE 1995, The steel market in 1994 and prospects for 1995, UNECE, Geneva. United States Geological Survey 2008, Salt statistics, . United States Geological Survey 2008, Salt, . United States Geological Survey 2008, U.S. Salt supply-demand relationships, November 6, 2009, . United States Geological Survey 2009, Soda ash in April 2009, Mineral Industry Surveys, . United States Geological Survey 2009, Soda ash, . Watt, S 2001, Chlorine, Marshall Cavendish, New York. Weller, O. & Dumitroaia, G. (2005): "The earliest salt production in the world: an early Neolithic exploitation in Poiana Slatinei-Lunca, Romania". Antiquity. Vol. 79. No. 306, November 5, 2009, . Windholz, M, Budavari, S, Stroumtsos, L Y & Fertig, M N 1976, Merck Index of Chemicals and Drugs. 9th edn. 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Other sources of rock salt worth noting are Chile, Egypt, Iran, Italy, Netherlands, Poland, Romania, Russia, Spain, Turkey, and Ukraine. 1.1.4 Market trends The production of rock salt has been increasing steadily with its increase in demand at the world market. The production in the United Kingdom has often reflected its market demand. In 1900, the United Kingdom consumed almost all its production. While the world production averaged about 12.2 million tonnes and world annual consumption in the first half of 1900 remained below 50 million tonnes, in the United Kingdom consumption was less than 6 million tonnes.

There was rapid increase, however, in the mid twentieth century of the world consumption that echoed the global production of about 109 million tonnes in 1965 and 210 million in 1999 (United States Geological Survey 2008), although in the United Kingdom the production and consumption remained somewhat steady at about 5 to 6 million tonnes per year. This capacity remained stable throughout to the 21st century (Brown et al. 2009, p.92). The prices of rock salt have also been experiencing an upward trend as years progress.

The price for one metric tonne of sodium chloride (or rock salt) stood at US$2.62 in 1900. This has risen to about US$33.40 in 2007. Historical prices of rock salt have shown consistent increases with each year, with some instances of price drop that are recovered in the following year. For instance, price of rock salt dropped by 4.3% to 19.80 per metric tonne in 1988, but regained its price to reach US$22 per metric tonne. While the price drop in 1991, 1995, 1997, 1998 have been in terms of cents (of the US dollar), the price increases have mostly been more than US$1.

However, in 2000 the price of rock salt decreased by US$1, while between 2005 and 2006 price of rock salt increased by US$3.04. Since 2000 the prices of rock salt have been on an upward trend, reaching US$33.40 in 2007 (United States Geological Survey 2008). In 2008, the United States consumed salt in the proportion of 38% for rock salt, 44% for brine, 10% for vacuum pan, and 8% for solar salt. Out of the total rock salt production, 40 percent was used in the chemical industry, while 90% of the rock salt used in feedstock was brine.

The caustic soda and chlorine industry have remained as the major consumer of rock salt in the United States. 1.1.5 Future Prediction The United Kingdom’s reserves for rock salt are extensive. The availability of rock salt, is therefore, sustainable to meet the future demands in UK. Its application to production of chlorine is, however, threatened due to the global trend in minimizing the use of chlorine. 1.2 Sodium Hydroxide, NaOH (caustic soda) 1.2.2 Physical and chemical properties Sodium Hydroxide has the molecular formula, NaOH.

It is normally a brittle, translucent white crystalline solid. It deliquesces when exposed to air, and resolidifies as a result of forming sodium carbonate upon absorption of carbon dioxide. Caustic soda is highly soluble in water. Sodium hydroxide releases heat when its concentrated solution is diluted, or when its solid form is dissolved in water. Its aqueous solutions are very alkaline, and it forms sodium salts in neutralization reactions. It reacts with certain metals and metal oxides to form complex anions and hydrogen.

It also reacts with gases like sulphur dioxide and carbon dioxide that form weak acids. 1.2.3 Sources Sodium hydroxide is co-produced with other products such as chlorine and soda ash. It is manufactured from rock salt in the same process that produce chlorine. The United States is the largest producer of caustic soda, with its production base in Wyoing and California(States Geological Survey 1998, p.156). There are several other sources of caustic soda in the world with Botswana, Kenya, Mexico, Turkey, and Uganda constituting some of the major producers. 1.2.

4 Market trend (Prices) The demand for sodium hydroxide in the United Kingdom has risen since the twentieth century but recent data indicates declines in consumption.

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