G-12 Chemistry U-3 Handout PDF

UN I T 3 INDUSTRIAL CHEMISTRY 3.1 Introduction  Industrial chemistry is a branch of chemistry which applies physical and chemical procedures toward the transformation of natural raw materials and their derivatives in to products...

UN I T 3 INDUSTRIAL CHEMISTRY 3.1 Introduction  Industrial chemistry is a branch of chemistry which applies physical and chemical procedures toward the transformation of natural raw materials and their derivatives in to products.  Industrial chemistry differs from classical chemistry in that it closes the gap created in concepts between chemistry as it is taught in schools, and chemistry as it is practiced commercially.  Industrial chemistry is the basis of the chemical industry.  The chemical industry is an institution involved in producing chemical products such as food, medicine, building materials, plastics, etc.  Generally, chemical industries  use naturally or artificially available raw materials to produce the desired products.  involve chemical reactions to transform raw materials into finished and semi-finished products.  consume relatively large quantities of energy during the manufacturing process.  use safe operation methods in their manufacturing processes. 3.2 Natural Resources and Industry 3.2.1 Natural Resources (Raw Materials)  Natural resources are the raw materials for the chemical industry which are obtained from the natural environment.  The raw materials are obtained from the different components of the natural environment. These are listed below From the atmosphere: The earth’s atmosphere has approximately 5 × 1015 tons of gases.  It is composed of different gases namely N2, O2, CO2, Ne, Ar, Kr and Xe.  They are important industrial raw materials. The natural supply of these gases is unlimited. From the hydrosphere: Ocean water which amounts to about 1.5 × 1021 liters contains about 3.5 percent by mass dissolved material. Seawater is a good source of sodium chloride, magnesium and bromine. From the lithosphere: The vast majority of elements are obtained from the earth’s crust in the form of mineral ores, carbon and hydrocarbons. Coal, natural gas and crude petroleum besides being energy sources are also converted to thousands of chemicals. From the biosphere: Vegetation and animals contribute raw materials to the so-called agro-based industries. Oils, fats, waxes, resins, sugar, natural fibers and leather are examples of thousands of natural products. Classification of Natural Resources  Natural resources can be classified as renewable and non-renewable resources. A. Renewable resources: The resources that can be replenished through rapid natural cycles are known as renewable resources.  These resources are able to increase their abundance through reproduction and utilization of simple substances. Examples; plants, (crops and forests) and animals which are being replaced from time to time because they have the power to reproduce and maintain life cycles.  There are also renewable resources without any life cycle. These include wood and wood-products, natural rubber, fibers (e.g.; cotton, jute, animal wool, silk, and synthetic fibers), pulp products, and leather.  Furthermore, resources, water, and soil are also classified as renewable resources.  Moreover, solar energy is considered a renewable resource as much as solar stocks are inexhaustible on the human scale. 1 B. Non-Renewable Resources: The resources that cannot be replenished (regenerated) through natural processes are known as non-renewable resources.  These are available in limited amounts and cannot be increased.  These resources include fossil fuels, minerals and salts.  Once a non-renewable resource is consumed, it is gone forever. A substitute for it is necessary. 3.2.2 Industry  Industry is a well-organized facility with a high degree of automation and specialization where large-scale manufacturing of goods take place. Manufacturing industry is a compartment of industry or economy which is concerned with the production or making of goods out of raw materials by means of a system of organized labor. Classification of manufacturing industry - Different types of products are manufactured. Chemical Industry: Chemical industry is a facility where industrial chemicals are manufactured. The products result from: a. Chemical reaction between organic materials, or inorganic materials, or both b. Extraction, separation, or purification of natural products, with or without the aid of chemical reactions c. The preparation of specifically valuable materials  Classification of the chemical industry based on raw material used for production 1. Chemical industries use natural raw materials (resources) Example: Sugar industries use sugar cane to manufacture sugar. 2. Chemical industries use products from other industries to manufacture their products. Example: Detergent and soap manufacturing industries use preprocessed products like caustic soda, caustic potash and related compounds to manufacture their products. Classification based on the product type Examples are:  Food processing industries  Beverages industries  Textiles industries  Wearing apparel industries  Leather industries  Paper products  Chemical industries etc. 3.3 Manufacturing of Valuable Products/ Chemicals Manufacturing of some valuable products: Manufacturing of valuable products involve a number of chemical processes.  The process is designed to produce a desired product from a variety of starting raw materials using energy through a succession of treatment steps integrated in a rational fashion.  The treatment steps could be either physical or chemical in nature.  Both organic and inorganic chemicals could be used in the manufacturing process. 2  3.3.1 Ammonia (NH3) Properties  Ammonia is lighter than air with a density of 0.769 kg/m3 at STP.  It is colorless with sharp and intensely irritating gas at room temperature.  Its solubility in water at 25 C0 is 34% (w/w).  Its melting point is -77.7 C0 and boiling point is -33.35 C0.  The most common commercial formulation is 28–30% NH3. Uses  Ammonia is an important compound, essential to man for a variety of diverse uses.  It is used as antimicrobial agent. NH3 in water is used as household cleaning agent and as a laboratory reagent.  It is used a raw material for the production of nitrogen fertilizers, raw material in the manufacturing of explosives such as nitrocellulose and trinitrotoluene (TNT). - TNT is used to generate charge transfer salts.  It is used in the production of soda ash and in the Ostwald process to get nitric acid etc. Such a diverse applicability has caused large demand for its production. Preparation  Ammonia is easily made in the laboratory by heating an ammonium chloride NH4Cl and sodium hydroxide or calcium hydroxide. 2NH4Cl + Ca (OH)2 → CaCl2 + 2H2O + 2NH3( g)  Ammonia is prepared industrially from nitrogen and hydrogen by the Haber process. N2 (g) + 3H2 (g) 2NH3 (g) 3.3.2 Nitric Acid Properties  Pure nitric acid is colorless, oily liquid and boils at 83 c0.  It is strong acid.  It is powerful oxidizing agent. Uses  Nitric acid is mainly used to make ammonium nitrate.  It is used to make explosive such as trinitrotoluene (TNT) and nitroglycerine.  It used for soil acidification in horticulture.  Another important application is rocket fuel. For this purpose, a mixture of HNO3, di nitrogen tetroxide and hydrogen peroxide, also known as red fuming nitric acid, is prepared.  Nitric acid’s potential for plastic production is also noteworthy.  Other less popular uses of nitric acid include:  production of organic dyes and lacquers;  pharmaceutical industry;  production of fungicides;  cleaning and etching of metal surfaces;  refining of precious metals for the jeweler industry (in preparation of aquaria);  the artificial ageing of wood to obtain the desired shade;  production of household cleaning products;  detection of traces of metals in laboratory test substances. 3  Preparation  Nitric acid is produced industrially from ammonia by the three-step Ostwald process  Steps in the Oswald process:  Oxidation of ammonia to nitric oxide 4NH3 (g) + 5O2 (g) 4NO (g) + 6H2O (l)  Oxidation of nitric oxide to nitrogen oxide 2NO (g) + O2 (g) 2NO2 (g)  Nitrogen dioxide dissolves in water to give nitric acid and nitric oxide, which can be captured and recycled. 3NO2 (g) + H2O (g) 2HNO3 (g) + NO (g)  In the laboratory, nitric acid is prepared by heating sodium nitrate with concentrated H2SO4 NaNO3 (aq) + H2SO4 (l) NaHSO4 (aq) +HNO3 (l) 3.3.3 Nitrogen-Based Fertilizers  The common forms of N-based fertilizer include anhydrous ammonia, urea, urea ammonium nitrate (UAN) solutions and Di ammonium Mono hydrogen Phosphate (DAP) with represented by chemical formula (NH4)2HPO4. Anhydrous Ammonia  Anhydrous ammonia (NH3) is the most basic form of nitrogen fertilizer.  Using a complex method called the Haber-Bosch process, nitrogen is captured from the air, combined with a hydrogen source and converted into a form that can be used by growing plants.  Ammonia in this form is also known as ammonia gas or anhydrous (“without water”) ammonia Application  Anhydrous ammonia is applied by injection 6 to 8 inches below the soil surface to minimize escape of gaseous NH3 into the air.  NH3 is a very hygroscopic compound and once in the soil, reacts quickly with water and changes to the ammonium (NH4+) form. As a positively charged ion, it reacts and binds with negatively charged soil constituents including clay and organic matter. Thus, it is held on the soil exchange complex and is not subject to movement with water.  Soil reactions - Over time and with appropriate soil temperatures that support biological activity, NH4+ ions are converted to the nitrate (NO3-) form by the action of specific soil bacteria in a process known as nitrification.  Nitrifying bacteria convert ammonia to nitrites or nitrates.  Denitrifying bacteria converts nitrates back to nitrogen gas.  Nitrification generally occurs at soil temperatures above 50 ℉, and increases as temperatures rise above this level. However, some limited activity occurs below 50 ℉ as well.  Ammonium is converted first to nitrite (NO2-) by the action of Nitrosamines bacteria, and then to nitrate by Nitrobacteria and Nitrosolobus bacteria: NH4+ Nitosomon NO2- NO2− Nitrobacteria NO3- Nitrosolobus 4  Urea  Urea is a solid fertilizer with high N content (46%) that can be easily applied to many types of crops and turf.  Its ease of handling, storage and transport, convenience of application by many types of equipment, and ability to blend with other solid fertilizers has made it the most widely used source of N fertilizer in the world. Production  Urea is manufactured by reacting CO2 with NH3 in the following two step reactions: 2NH3 + CO2 → NH2COONH4 (ammonium carbamate) NH2COONH4 → (NH2)2 CO + H2O (urea + water)  The urea molecule has 2 amide (NH2) groups joined by a carbonyl (C=O) functional group.  Urea readily dissolves in water, including soil moisture. It can be “incorporated” into the soil by sufficient rainfall or irrigation.  Soil Reactions - If urea is applied to the soil surface and not incorporated by water or tillage, it is subject to volatilization losses of nitrogen. This occurs as urea undergoes hydrolysis to carbon dioxide and ammonia: (NH2)2CO + H2O → CO2 + 2NH3 Urea-ammonium nitrate (UAN) Solutions  Urea-ammonium nitrate (UAN) solutions are also popular nitrogen fertilizers.  These solutions are made by dissolving urea and ammonium nitrate (NH4NO3) in water.  Urea-ammonium nitrate (UAN) solutions are mixtures of urea, ammonium nitrate, and water in various proportions.  All common UAN solutions (28%, 30% and 32%) are formulated to contain 50% of actual N as amide, (from urea), 25% as ammonium (from ammonium nitrate), and 25% as nitrate (from ammonium nitrate). Production  Liquid urea-ammonium nitrate (UAN) fertilizer is relatively simple to produce.  A heated solution containing dissolved urea is mixed with a heated solution of ammonium nitrate to make a clear liquid fertilizer.  Half of the total nitrogen comes from the urea solution and half from the ammonium nitrate solution. Soil Reactions - The urea portion of UAN solutions reacts just as dry urea does (see the reaction of urea).  If applied on the surface, the amide-N in the solution may incur losses due to volatilization when urease hydrolysis releases NH3. But if UAN is incorporated by tillage or sufficient water, the NH3, quickly reacts with soil water to form NH4+.  This ammonium, as well as the ammonium nitrogen derived from ammonium nitrate in the solution, adhere to soil components at the application site and is not subject to loss in the short term.  Like N applied as anhydrous ammonia, this nitrogen will eventually be taken up by plants in the ammonium form, or if not, eventually converted to nitrate by soil bacteria. Diammonium Monohydrogen Phosphate (DAP), (NH4)2HPO4  Diammonium monohydrogen phosphate (DAP) is a white crystalline compound. Production  Diammonium monohydrogen phosphate (DAP) is formed by the reaction between ammonia and phosphoric acid by the following two steps: Step 1: Anhydrous ammonia reacts with phosphoric acid to form monoammonium dihydrogen phosphate and diammonium monohydrogen phosphate 3NH3 (g) + 2H3PO4 (l) → NH4H2PO4 (s) + (NH4)2 HPO4 (s) Step 2: Recycling monoammoniumdihydrogen phosphate for further reaction with anhydrous ammonia yields DAP: NH4H2PO4 (s) + NH3 (g) → (NH4)2 HPO4 (s) 5  DAP is used as a fertilizer. It temporarily increases soil acidity, but over the long term, the soil becomes more acidic than before upon nitrification of the ammonium.  DAP has the advantage of having both nitrogen and phosphorus, which are essential for plant growth.  DAP can be used as fire retardant. It lowers the combustion temperature of the material, decreases weight-loss rates, and causes an increase in the production of residue or char.  DAP is also used as a yeast nutrient in wine making and beer brewing. 3.3.4. Sulphuric Acid Properties  Anhydrous, 100% sulphuric acid is a colorless, odorless, heavy, oily liquid.  It is heavier than water, with 98 gram/mole molar mass.  Pure H2SO4 melts at 10.5 °C and boils at 338 °C. It is soluble in all ratios with water.  This chemical is highly corrosive and reactive.  The dissolution of sulfuric acid in water is very exothermic i.e. a large amount of heat is released and the solution may even boil.  It has a very high oxidizing power and acts as a strong oxidizing and dehydrating agent.  It can oxidize both metals as well as non-metals.  It itself reduces to sulphur dioxide. Example: Cu + 2H2SO4 → CuSO4 + SO2 + H2O 2H2SO4 + C → 2SO3 + CO2 + 2H2O  33.5 % sulphuric acid commonly called battery acid while 62.18 sulphuric acid is known as chamber acid used for production of fertilizers.  “Sulfuric acid (H2SO4) is the largest volume chemical produced in the world. It is normally manufactured twice the amount of any other chemical and is a leading economic indicator of the strength of many industrialized nations. The rate of consumption of sulphuric acid is a measure of a country’s industrialization”.  Sulphuric acid is soluble in all ratios with water. Preparation  Sulphuric acid is manufactured industrially by the contact Process which involves the following four major steps: Step 1: Burning sulphur in air (preparation of sulphur dioxide): S (s) + O2 (g) → SO2 (g) Step 2: Converting SO2 to SO3 (Oxidation of sulphur dioxide to prepare sulphur tri oxide) 2SO2 (g) + O2 V2O5 2SO3 (g) Step 3: Passing SO3 into concentrated H2SO4 (reaction to give oleum): SO3 (g) + H2SO4 (l) → H2S2O7 (l)  Sulphur trioxide is absorbed into 98 % sulphuric acid to form oleum which is also known as fuming sulphuric acid. Step 4: Addition of water to oleum i.e. Dilution of oleum to produce concentrated sulphuric acid H2S2 O7 (l) + H2O (l) → 2H2SO4 (l)  Oleum is diluted with water to form concentrated sulphuric acid. Uses  In the fertilizer industry:  It is used in the preparation of fertilizers such as ammonium phosphate, ammonium sulphate, super phosphate of lime, etc. 6  In the petroleum refining:  It is used for the refining of crude petroleum.  In the chemical industry:  It is used for the manufacture of hundreds of other compounds such as hydrochloric acid, nitric acid, phosphoric acid, sulphates, bisulphates, diethyl ether, etc.  In metallurgy:  Sulphuric acid is used for metallurgical processes such as electrolytic refining, electroplating, galvanizing, etc. A number of metals like copper, silver, etc. are extracted from their ores using sulphuric acid.  It is used for cleaning the surfaces of metals (picking) before electroplating.  It is used in the manufacture of explosives such as dynamite, T.N.T. nitro cellulose products (gum, cotton), etc.  It is also used as a drying and dehydrating agent. It is often used to dry neutral and acidic gases such as nitrogen, oxygen, and carbon dioxide.  It is used for storage batteries as an electrolyte. 3.3.5 Some Common Pesticides and Herbicides Pesticides  Pesticides are chemicals used to prevent or control pests, diseases, weeds and other plant pathogens.  Chemical pesticides can be classified according to their chemical composition. Types of pesticides:  Insecticides (killing insects)  Herbicides (killing plants)  Fungicides (killing fungus)  Rodenticides (killing rodents, like mice and rats)  Bactericides (killing bacteria) Insecticide: any toxic substance that is used to kill insects. Such substances are used] primarily to control pests that infest cultivated plants or to eliminate disease carrying insects in specific areas.  This method allows the uniform and scientific grouping of pesticides to establish a correlation between structure, activity, toxicity and degradation mechanisms, among other characteristics.  Table 3.1, shows the most important pesticides and their general characteristics, and Figure 3.11 show examples of some chemical structures of pesticides.( see your text book)  On the other hand, there are also traditionally produced pesticides by Ethiopian farmers.  Traditionally, farmers of different districts produce pesticides from botanical origins and then apply it to fruits, vegetables and other crops.  These pesticides are called botanical pesticides.  Botanical pesticides are extracted from various plant parts (stems, seeds, roots, leaves and flower heads) of different plant species. Botanical  The following are some of the common natural pesticides commonly used in some areas of Ethiopia: Neem Leaf, Salt Spray and Onion and Garlic Spray. Neem Leaf  Neem has long been used for its medicinal and culinary properties.  It is also known to be used as a deterrent to pests. This medicinal herb has a bitter taste and strong odor that may keep the bugs away from your plants, but non-toxic to animals, birds, plants and humans.  It's best to spray Neem oil on young plants where it is said to be effective for about 22 days. Herbicides (chemical weed killers)  Herbicides also commonly known as weed killers which are substances used to control unwanted plants. 7   Selective herbicides control specific weed species, while leaving the desired crop relatively unharmed.  Non-selective herbicides (sometimes called total weed killers in commercial products) since they kill all plant material with which they come into contact.  Herbicides have largely replaced mechanical methods of weed control in countries where intensive and highly mechanized agriculture is practiced. Types of Herbicides 3.3.6 Sodium Carbonate Properties  Sodium carbonate (washing soda) is a white crystalline solid powder.  It exists as a hydrate (Na2CO3.10H2O) compound.  It has a density of 2.54 g/cm3, a purity of > 98 %.  It has a high melting point 851°C and a high boiling point 1,600 °C.  It has hygroscopic properties in nature.  There are two forms of sodium carbonate available, light soda and dense soda.  Light soda and dense soda are both chemically identical compounds, with the only difference being their densities and size.  Light soda has a lower density of 0.7 g/ml, while dense soda has about 0.9 g/ml.  Sodium carbonate can be easily dissolved in water to form an aqueous solution with moderate alkalinity and dissolved in acids by liberating CO2. But it is insoluble in alcohol.  Anhydrous Sodium Carbonate is unaffected by heat.  It melts without disintegrating.  The release of OH–(aq) ions during hydrolysis makes Sodium Carbonate aqueous solutions somewhat alkaline. Na2CO3 (s) + 2H2O (l) → H2CO3 (aq) + 2Na+ (aq) + 2OH- (aq)  Its aqueous solution has the property of absorbing carbon dioxide from the air, and produces sodium hydrogen Carbonate. Na2CO3 (aq) + H2O + CO2 (g) → 2NaHCO3 (aq) Uses  One of the most important applications of sodium carbonate is for the manufacturing of glass.  During the production of glass, sodium carbonate acts as a flux in the melting of silica.  It is largely used in production of detergents and soaps.  It is used in the manufacturing of pulp and paper, textiles, drinking water.  It can also be used for tissue digestion, dissolving amphoteric metals and compounds, food preparation as well as acting as a cleaning agent.  It is also used in the brick industry. 8  Brine treatment and water purification Production Method (Solvay process)  Sodium carbonate at present is mostly mined from its natural deposits.  It also is manufactured synthetically by Solvay (or ammonia-soda) process.  The natural production of sodium carbonate currently has surpassed its synthetic production.  The Solvay process involves a series of partial reactions.  The first step is calcination of calcium carbonate to form lime and CO2. 1. CaCO3 → CaO + CO2 2. CaO + H2O → Ca(OH) 2 3. 2NaCl + 2CO2 + 2NH3 + 2H2O → 2NaHCO3 + 2NH4Cl 4. 2NaHCO3 → + H2O + CO2 + Na2CO3 5. Ca( OH)2 + 2NH4Cl → CaCl2 + 2NH3 + 2H2O The overall reaction: 6. CaCO3 + 2NaCl → Na2CO3 + CaCl2 3.3.6 Sodium Hydroxide (NaOH)  Properties  It is commonly known as caustic soda or lye.  Sodium hydroxide (NaOH) is a white, translucent crystalline solid with a melting point of 591 k.  It is a stable compound.  It decomposes proteins at room temperatures and may cause chemical burns to human bodies.  It dissolves readily in water and moderately soluble in alcohol; its solution has bitter and has a soapy feeling”.  It is strongly alkaline in nature commonly used as a Base. Manufacturing process  NaOH does not occur in nature.  It has been manufactured at large scale for many years from readily obtainable raw materials.  It is manufactured from sodium chloride (NaCl) and water (H2O) in electrolysis process.  Its preparation involves various methods like; 1. Castner-Kellner process 2. Nelson Diaphragm cell 3. Loewig’s process Castner-Kellner process Principle: In the Castner-Kellner method, electrolysis of brine solution is performed in order to obtain sodium hydroxide. Castner-Kellner cell: It is a steel tank that is rectangular. Ebonite is lined inside the tank.  Titanium acts as an anode and a layer of mercury at the bottom of the tank acts as the cathode.  Ionization of brine solution occurs according to the following reaction: 2NaCl → 2Na+ + 2Cl− When the brine solution comes in contact with electric current, ionization takes place.  As a result positive and the negative ions move towards the electrodes. Sodium ions get deposited at the mercury cathode forming a sodium amalgam.  Chlorine ions move towards the anode and exit the cell from the top. Reaction at the anode: 2Cl− → Cl2 + 2e− Reaction at the cathode: 2Na+ + 2e− →2Na 9  Formation of NaOH  The amalgam formed is then transferred to another chamber called denuder. In the denuder, it is treated with water to obtain a sodium hydroxide solution.  On evaporation of the solution, solid sodium hydroxide is formed. This is a very efficient process in order to obtain pure caustic soda.  Mercury is toxic so care must be taken to prevent mercury losses. Safety  Due to its strong corrosive qualities, exposure to sodium hydroxide in its solid or solution form can cause skin and eye irritation  Pure NaOH has a high affinity for water and may form hydrates depending on the concentration. Since some hydrates have melting points greater than 0 °C, insulation or heating during storage. Uses  It is used manufacturing of soap, detergents, pulp, textile and paper.  Alumina extraction from bauxite in aluminum production.  Removing sulphur from petroleum 3.4. Some Manufacturing Industries in Ethiopia List of some industries in Ethiopia NO Industry Product Location 1 Mesobe Cement Factory Cement Tigray 2 Muger Cement Factory Cement Muger 3 Dire Dawa Cement Factory Cement Dire Dawa 4 Derba Midroc Cement Factory Cement Northern Shewa 5 Nifas Silk Paint Factory Paint A.A 6 Dil Paint Factory Paint A.A 7 Tsedy Paint Factory Paint A.A 8 Repi Soap and Detergent Factory Soap and Detergent A.A 9 Gulele Soap Factory Soap A.A 10 Nazreth Soap Factory Soap Nazreth (Adama 11 Fincha Sugar Factory Sugar Fincha 12 Metehara Sugar Factory Sugar Metehara 13 Wonji Sugar Factory Sugar Wonji 14 Matador Addis Coma Factory Tyres A. A 15 Saint George Brewery Beer A. A 16 Bedelle Brewery Beer Bedelle 17 Meta Brewery Beer Sebeta 18 Harar Brewery Beer Harar 19 Dashen Brewery Beer Gondar 20 Awash Tannery Processed Leather A. A 21 Mojo Tannery Processed Leather Mojo 22 Addis Foam and Plastic Factory Plastic A. A 23 Ethio Plastic Plastic A.A 24 Adamitulu Pesticide Factory Pesticides Adamitulu 25 Caustic Soda factory Caustic Soda Hawassa 26 Tabor Ceramic Factory Ceramics Hawassa 27 Sulfuric Acid and Aluminum Sulphate Sulfuric Acid and Awash Melkassa Factory Aluminum Sulphate 28 Ethio Gas and Carts Plastics arts and CO2 A. A 10  29 Chora Gas and Chemical Products Oxygen, Acetylene, Shoe A.A polish, floor wax 30 Addis Glass Factory Glass A. A 31 Nas Foods Factory Biscuits A.A 32 Arbaminch Textile Factory Textile Arbaminch 33 Almeda Textile Factory Textile Tigray (Adowa) 3.4.1 Glass Manufacturing  Glass is an amorphous or non-crystalline solid material.  It is inexpensive to make, easy to shape when it’s molten.  It can be recycled any number of time.  The main component of glass is silica. Types of glass Quartz glass- is made from pure silica, SiO2, at a temperature of about 2300°C.  It is of high strength, low thermal expansion and highly transparent. Soda-lime glass- is ordinary glass.  It is a mixture of sodium silicate and calcium silicate.  It is made by heating a mixture of silica sand, sodium carbonate or sodium sulphate and limestone.  The reactions that take place in forming soda-lime glass are: Na2CO3 + SiO2 → Na2SiO3 + CO2 CaCO3 + SiO2 →CaSiO3 + CO2  Soda-lime glass accounts for about 90% of manufactured glass.  Widely used for window panes, bottles, dishes etc.  Borosilicate glass- is commonly known as Pyrex.  It is manufactured using boron (III) oxide (B2O3).  High resistance to chemical corrosion and temperature changes.  Widely used to make ovenware and laboratory equipment such as flasks, beakers, and test tubes.  Colored glass is obtained by the addition of metallic oxides. Example of Some substances and the color the impact to glass Substance added The color of the glass Cobalt(II) oxide Blue Ferrous compounds Green Cadmium sulphide Yellow Chromium (III) oxide Green Cupric oxide Green Sulphur Amber Steps in glass production 1. Batch preparation- the raw materials preparation.  The raw materials are mixed in a proportion of 60% sand, 21% sodium carbonate and 19% limestone. 2. Glass melting- melting raw materials and recycled glass (according to their color) at 1600°C.  The furnace operates continuously, producing glass 24 hours a day. 3. Glass forming-changing into a required shape. 4. Annealing- removal of internal stresses by reheating the glass followed by a controlled slow-cooling cycle. 5. Inspection- testing the quality of glass. 6. Packing and dispatching is the final stage before distribution 11  3.4.2 Ceramics  Ceramic is an inorganic, non-metallic solid prepared by heating minerals to high temperature and then cooling.  Traditional ceramics, such as porcelain, tiles, and pottery are formed from minerals such as clay, talc and feldspar.  Modern ceramics are formed from extremely pure powders of specialty chemicals, such as silicon carbide, alumina, barium titanate, and titanium carbide. Manufacturing of Ceramics  The mineral used to make ceramics is first crushed and ground to a fine powder.  Then it purified powder by mixing it in a solution and allowing a chemical to form precipitate (a uniform solid that forms within a solution).  The precipitate is then separated from the solution and heated to drive off impurities including water. The steps of manufacturing ceramics include: A. Moulding  The crushed fine powder, small amounts of wax is added to bind the ceramic powder and make it more workable.  Plastics may also be added to the powder to give the desired pliability and softness.  The powder can be shaped into different objects by various moulding processes. B. Densification  The ceramic object is heated in an electric furnace to temperatures between 1000 °C and 1700 °C.  As the ceramic heats, the powder particles coalesce, much as water droplets join at room temperature.  As the ceramic particles merge, the object becomes increasingly dense, shrinking by up to 20 percent of its original size.  The goal of this heating process is to maximize the strength of ceramic by obtaining an internal structure that is compact and extremely dense.  In general, most ceramics are hard and wear-resistant, brittle, refractory, thermal and electrical insulators, non-magnetic, oxidation-resistant, and chemically stable.  Due to the wide range of properties of ceramic materials, are used for a multitude of applications. Well-known uses of ceramics: - they are commonly found in art sculptures, dishes, platters, and other kitchenware, kitchen tiles and bath room structures. Lesser-known uses for ceramics: - they are used as electrical insulators, computer parts, tools, dental replacements, engine parts, and tiles on space shuttles and to replace bones such as the bones in hips, knees, and shoulders. Future uses of ceramics: - In the future, ceramics might be used to remove impurities from the drinking water and to replace diseased heart valves. 3.4.3 Cement  The raw materials for the production of cement are limestone, clay, silica sand, gypsum, calcium silicate, calcium aluminate, iron (III) oxide, magnesium oxide and pumice.  Cement mainly contains calcium silicate (CaSiO3) and calcium aluminate (Ca (AlO2)2). Manufacturing Process  Cement is made by heating limestone (chalk), alumina (Al2O3) and silica-bearing materials such as clay to 1450 °C in a kiln. This process is known as calcination.  Calcination results a hard substance called clinker. The clinker is then ground with a small amount of gypsum into a powder. The resulting cement is known as Ordinary Portland cement (OPC).  Portland cement was first discovered in England. 12   When cement is mixed with water it forms a plastic mass that hardens after some time.  Upper Part of the Kiln Raw Material → complete elimination of moisture  Middle Part of the Kiln Limestone decomposes to calcium oxide CaCO3 (s) CaO(s) + CO2 (g)  Lower End of the Kiln Setting of Cement  When cement mixed with water, the cement first forms a plastic mass that hardens after sometime. This is due to the formation of three-dimensional cross-links between –Si–O–Si– and –Si–O– Al– chains.  The first setting occurs within 24 hours, whereas the subsequent hardening requires about two weeks. In the hardening process of cement, the transition from plastic to solid state is called setting. 3.4.4 Sugar Manufacturing  Sugar is prepared from sugar cane Steps in sugar production 1. Collecting the harvest – cutting matured cane and transport. 2. Cleaning and grinding – crushing the sugar cane.  During grinding, hot water is sprayed onto the sugarcane to dissolve the remaining hard sugar. 3. Juicing- removing pulp or bagasse.  Sugarcane travels on the conveyor belt through a series of heavy-duty rollers which extract juice from the pulp.  The pulp that remains, or “bagasse”, is dried and used as a fuel. 4. Clarifying – removing non – sugar debris by adding CO2  Carbon dioxide and milk of lime are added to the liquid sugar mixture, which is heated until boiling.  Carbon dioxide moves through the liquid, it forms calcium carbonate which attracts non-sugar debris (fats, gums and waxes) from the juice, and pulls them away from the sugar juice. 5. Evaporation – removal of water to form brown syrup. 6. Crystallization – removal of water from sugar syrup.  The crystals are sent to a centrifuge that spins and dries them.  The dried product is raw sugar, which is edible. 7. Refinery – purification and bleaching sugar  Raw sugar is mixed with a solution of sugar and water to loosen the molasses from the outside of the raw sugar crystals, producing a thick matter known as “magma”.  The crystals are promptly washed, dissolved and filtered to remove impurities.  The golden syrup that is produced is then sent through filters, and SO2 is passed through it to remove the color and water and the process is known as bleaching. 8. Separation and packaging - final evaporation and drying process is done. 13  3.4.5 Paper and Pulp  Paper is not a chemical compound which can be expressed by a chemical formula.  Paper is a mixture made from rags and wood pulp glued together with some additives, bleached and dried.  Wood pulp is made from soft-wood trees, such as spruce, pine, fir, larch and hemlock, and from hard woods, such as eucalyptus, aspen and birch.  Wood is composed of cellulose, lignin, oils and resins. Lignin is used to bind fibers of cellulose together.  To provide wood pulp, the cellulose must be separated from the lignin. Manufacturing of pulp and paper involves the following steps  Harvesting: trees involve the cutting down of trees from their growing areas.  Preparation: for pulping is a step in which the bark of the tree is removed and then the wood is chipped and screened to provide uniform sized chips (pieces). Pulping is a step used to make wood pulp from the chipped wood pieces.  This can be accomplished by either mechanical or chemical means depending on the strength and grade of paper to be manufactured. A. Mechanical pulping: It utilizes steam, pressure and high temperatures instead of chemicals to tear the fibers.  The fiber quality is greatly reduced because mechanical pulping creates short, weak fibers that still contain the lignin that bonds the fibers together.  Paper used for newspapers are a typical product of mechanical pulping. B. Chemical pulping: Chemical pulp is produced by combining wood chips and chemicals in large vessels called digesters.  Heat and the chemicals break down the lignin which binds the cellulose fibers together without seriously degrading the cellulose fibers.  Chemical pulp is manufactured using the Kraft process or the Sulphite Process. a. The Kraft Process is the dominant chemical pulping method.  It is the most widely used method for making pulp from all types of trees.  The process uses aqueous sodium hydroxide and sodium sulphide as a digestion solution. Wood chips + NaOH + Na2S ------> Black Liquor  After digestion for about four hours at a temperature of 170 ℃, the pulp is separated by filtration  This process uses a basic digestion medium. b. The Sulphite Process uses a cooking liquor (digestion) solution of sodium bisulphate or magnesium bisulphate digester at pH of about 3 in a pulp.  The action of the hydrogen sulphide ions at 60 ℃ over 6 to 12 hours dissolves the lignin and separates it from the cellulose.  After the process is complete, the pulp is recovered by filtration.  The wood pulp achieved from the Sulphite or Kraft processes is washed to remove chemicals and passed through a series of screens to remove foreign materials. 4. Bleaching: It is the process of removing coloring matter from wood pulp and increasing its brightness.  The most common bleaching agents are strong oxidizing agents such as chlorine, chlorine oxide, ozone and hydrogen peroxide. 5. Making paper from pulp: the pulp is processed into liquid stock that can be transferred to a paper mill. 6. The suspension is poured onto a continuously moving screen belt and the liquor is allowed to seep away by gravity to produce paper sheet. 7. The continuous sheet then moves through additional rollers that compress the fibers and remove the residual water to produce fine paper. 14  3.4.6 Tannery  Tanning is a process of converting raw animal hides and skin to leather, using tannin.  Tannin is an acidic chemical that permanently alters the protein structure of skin so that it can never return to raw hide or skin again.  Leather production involves various preparatory stages, tanning, and crusting 1. Preparatory stages are those in which the hide or skin is prepared for tanning.  This stage includes curing, soaking, flesh removal, hair removal, scudding, and deliming. a. Curing - is process involves salting or drying the hide to prevent bacterial infection and dehydrate the skin.  Brine curing is the simplest and fastest method. b. Soaking- is process, cured hides are soaked in water for several hours to several days to remove salt, dirt, debris, blood and excess animal fat from the skin and make the skin soft. c. Flesh removal- is process; remove unwanted flesh from the skin by machine. d. Hair removal- the soaked hides are immersed in a mixture of lime and water. This process is called liming.  It loosens the hair from the skin and makes hair-removal easier. e. Scudding- is the process in which hair and fat missed by the machines are removed from the hide with a plastic tool or dull knife. f. Deliming- is process involves the removal of lime from the skin or hides in a vat of acid. 2. Tanning is a process that converts the protein of the raw hide or skin into a stable material.  There are two main types of tanning: a. Vegetable or natural tanning- the skin is placed in a solution of tannin.  Tannins occur naturally in the barks and leaves of many plants.  The primary barks used in modern times are chestnut, oak, tanoak, hemlock, quebracho, mangrove, wattle (acacia) and myrobalan.  Naturally tanned hide is flexible and is used for making shoes, luggage and furniture. b. Mineral tanning- the skin is placed in solutions of chemicals such as chromium sulphate and other salts of chromium.  Chrome tanning is faster than natural (vegetable) tanning and requires only twenty four hours.  The leather is greenish-blue in color derived from the chromium.  This process produces stretchable leather that is used for making garments and handbags. 3. Crusting- is the final stage in leather manufacturing and includes dyeing, rolling the leather to make it strong, stretching it in a heat-controlled room and performing a process that involves covering the grain surface with chemical compounds such as wax, oil, glazes etc. to make the leather very attractive. 3.4.7 Food Processing and Preservation  Food preservation is the process of treating and handling food to stop or greatly reduce spoilage, loss of quality, edibility or nutritive value caused or accelerated by microorganisms.  Preservation usually involves preventing the growth of bacteria, fungi and other microorganisms, as well as reducing the oxidation of fats which causes rancidity. Modern methods of food preservation are: A. Freezing: is used to preserve prepared foods that do not require freezing in their normal state. Example: potatoes B. Freeze-drying- involves the gentle escape of water vapor.  The process leaves the product close to its original shape, taste, and color and there is no loss of aroma or flavor. 15  For example, liquids such as coffee, tea, juices and other extracts, vegetables, segments of fish and meat products.  Freeze-drying is a superior preservation method for a variety of food products and food ingredients. C. Vacuum-packing- Stores food in a vacuum environment, usually in an air-tight bag or bottle.  The vacuum environment strips bacteria of the oxygen needed for survival, slowing down the rate of spoiling.  Vacuum-packing is commonly used for storing nuts to reduce loss of flavor from oxidation. Inorganic and organic preservatives  Some inorganic and organic preservatives are available for food preservation.  Some examples of inorganic preservatives are sodium chloride (NaCl), nitrate and nitrite salts, sulfites, and sulfur dioxide (SO2).  NaCl lowers water activity and causes plasmolysis by withdrawing water from cells.  Nitrites and nitrates are curing agents for meats (hams, bacons, sausages, etc.) to inhibit Clostridium botulin under vacuum packaging conditions.  Sulfur dioxide (SO2), sulfites (SO3), bisulfite (HSO3-2), and met bisulfites (S2O5-2) form sulfurous acid in aqueous solutions, which is the antimicrobial agent.  Sulfites are widely used in the wine industry to sanitize equipment and reduce competing microorganisms.  Wine yeasts are resistant to sulfites.  Sulfites are also used in dried fruits and some fruit juices.  Sulfites have been used to prevent enzymatic and no enzymatic browning in some fruits and vegetables (cut potatoes).  A number of organic acids and their salts are used as preservatives.  These include lactic acid and lactates, propionic acid and propionates, citric acid, acetic acid, sorbic acid, and sorbates, benzoic acid and benzoates, and methyl and propyl parabens (benzoic acid derivatives). For example, propionic acid and propionate salts (calcium most common) are active against molds at pH values less than 6.  They have limited activity against yeasts and bacteria.  They are widely used in baked products and cheeses.  Acetic acid is found in vinegar at levels up to 4–5%.  It is used in mayonnaise, pickles, and ketchup, primarily as a flavoring agent.  Acetic acid is most active against bacteria, but has some yeast and mold activity, though less active than sorbates or propionates. 3.4.8 Manufacturing of Ethanol  Ethanol is one of the constituents of all alcoholic beverages. ‘Tella’, ‘Tej’, beer, wine, ‘Katikalla’, ouzo, gin and whisky contain ethanol.  There are a number of methods for preparing ethanol using different materials. Industrial preparation of Ethanol  Ethanol is manufactured industrially by: 1. Fermentation of carbohydrates such as sugar:  Fermentation is the slow decomposition of carbohydrates such as sucrose, starch and cellulose in the presence of suitable enzyme that results in the formation of ethanol and carbon dioxide. 16  Fermentation can produce an alcoholic beverage whose ethanol content is 12 – 15% only. The alcohol kills the yeast and inhibits its activity when the percentage is higher. To produce beverages of higher ethanol content, distillation of the aqueous solution is required. Most liquor factories in Ethiopia use molasses, a by-product of sugar industries, as a raw material to produce ethanol.  In the brewing industry, germinated barley called malt (in Amharic, ‘Bikil’) is used as the starting material.  The whole process taking place in breweries is summarized as follows: 2. Catalytic Hydration of Ethene:  Most ethanol is manufactured at present by this method.  In this process, ethene is treated with steam at 573 K and 60 atm pressures in the presence of phosphoric acid, H3PO4, catalyst. Beer  The raw materials for beer are barley and hops.  The first step is to bring the barley to germination whereby starch is converted into a type of sugar called malt sugar.  Heat stops this process and the material is now called malt.  After drying and grinding the barley, water is added in the mash tubes.  After adding hops and yeast the process of fermentation begins.  Then it is stored in tanks for a period of time as required by a type of the product.  Later it is pasteurized and carbon dioxide is added under pressure and supplied to consumers.  The average beer has alcohol content between 2-6 % by volume. Wine  Grapes are the most common raw materials for producing wines.  Grapes (or tether fruits) are first crushed and then steamed.  The liquid that is derived from the crushing process is called must.  It then goes to a fermentation takes place.  The must then passes to a settling tank where sediment is allowed to settle, and proceeds from there to a filter.  The clear liquid is cooled in a refrigerator tank and it is pasteurized as it passes through a flash pasteurizer. 17   It finally goes to a storage tank where it is kept for months or years.  The older a wine is kept, the more mature it becomes and usually is considered to have a higher quality fetching higher price.  Most wines have an alcohol content varying from 10-16 per cent by volume. Liquor  Compared with beer and wine liquor contains a higher percentage of pure alcohol.  To get drinks with higher concentration of alcohol the alcohol has to be separated from the solution by distillation.  Liquors (e.g. cognac) are made by distillation of grape wine; rum is produced from sugar cane, and whisky from rye.  Different types of liquors have different alcohol concentration.  Most of them however range between 30-45 percent of alcohol by volume. Local Preparation of Ethanol (Araki)  Araki is the local Ethiopian alcohol which is prepared almost everywhere with certain local differences.  In fact, the differences are in the ingredients and not in the process of making it.  First, the barley is made into “Bikel”.  The help of water, the Bikel is mixed with Gesho powder to make starter “Tinses”.  The starter is left to ferment for about four days, (It depending upon the local’s humidity and temperature).  The bread is baked from ingredients of Teff, Barley, Wheat, and Sorghum, depending upon their availability and local preferences.  The bread is broken down into small pieces, mixed with prepared starter and left to stand to ferment for a couple of days (5 to 10 days).  After it is fully fermented, a proportional amount of water is added to liquidity the tick dough-like mixture and left for 1 to 2 days for further fermentation.  Finally, the liquid mixture is boiled and distilled in the traditional ways.  The distillate is called “Araki”. While the leftover residue or the un-distilled component is locally called “Atela” and it is usually used to feed cattle. 3.4.9 Soap and Detergent Soaps  Soaps are metallic salts of higher fatty acids.  Animal fat and vegetable oils are used for manufacturing soap.  Fats and oils are naturally occurring esters of glycerol and the higher fatty acids.  Soaps are substances used to remove dirt.  They are also called surfactants or surface-active agents, because they reduce the surface tension of water and change the surface properties.  Soaps are either sodium or potassium salts of higher (long-chain) carboxylic acids.  Soaps that are sodium salts are called hard soaps and potassium salts are soft soaps.  Soaps are prepared by boiling animal fat or vegetable oil with a base.  The reaction that produces soap is called saponification. 18  In industry, tallow, lard, cotton seed oil, palm oil, castor oil, olive oil, whale oil and the oil of soybeans are used to prepare ordinary soap. The structure of soap  The long covalent hydrocarbon chain gives rise to the hydrophobic (water hating) and oil-soluble (non-polar) properties of the soap molecule  The charged carboxylate group is attracted to water molecules (hydrophilic). In this way, soaps are composed of a hydrophilic head and a hydrophobic tail:  In solution a soap molecule consists of a long non-polar hydrocarbon tail (e.g. C17H35-) and a polar head (-COO-). Industrially soap is produced in four basic steps 1. Saponification- A mixture of tallow (animal fat) or coconut oil is mixed with sodium hydroxide and heated.  The soap produced is the salt of a long chain carboxylic acid 2. Glycerin removal- glycerin is more valuable than soap, so most of it is removed.  Some is left in the soap to help make it soft and smooth.  Soap is not very soluble in salt water, whereas glycerin is, so salt is added to the wet soap causing it to separate out into soap and glycerin in salt water. 3. Soap purification - Any remaining sodium hydroxide is neutralized with a weak acid such as citric acid and two thirds of the remaining water removed. 4. Finishing-Additives such as preservatives, color and perfume are added and mixed in with the soap and it is shaped into bars for sale. 19  ADVANTAGES: Soaps are eco-friendly and bio degradable DISADVANTAGES:  Soaps are not suitable in the hard water  They have weak cleansing properties than detergents. Detergents  Detergents are sodium salts of sulphonated long chain organic alcohols, R-C6H4SO3 Na, where: R is an alkyl group with a chain of 10 to 18 carbon atoms.  The water-soluble group is –SO3Na while the fat soluble one is the –R-C6H4 groups.  They are called soap less soaps because they lather well; they are very different from ordinary soaps in their chemical composition.  Long open chain alcohols and alkyl benzene sulphonic acid can be used for the production of detergents  The advantage of detergents - is lather well with both soft and hard water and even with water that contains common salt or acids.  They are more soluble than soap in water, form stable emulsions with grease and do not form a scum with hard water because their calcium and magnesium salts are soluble. Example  Sodium lauryl sulphate or sodium n-dodecyl sulphate is prepared first by reacting dodecyl (lauryl) alcohol with sulphuric acid followed by reaction with sodium hydroxide.  The reaction equation is: DISADVANTAGES OF DETERGENTS -they are not biodegradable and elimination from municipal wastewaters by the usual treatments is a problem. Surfactants used for their preparation pose a danger to aquatic life. CLEANSING ACTION OF DETERGENTS  The cleansing action of detergent and soap is fundamentally same.  When a detergent dissolves in water, its molecule will dissociate to form sodium or potassium ion and detergent ion (detergent anion).  The detergent ion such as R-O-SO3- can be represented in a simplified form by structure below. 20  Dry Cleaning  Dry cleaning refers to the use of different chemicals that are capable of dissolving grease and other dirt stains in a similar manner as soaps without the use of water.  The most commonly used chemicals in dry cleaning are organic chemicals such as tetra chloromethane, CCl4; tetra chloroethylene, Cl2C = CCl2; benzene and gasoline. Example: Silk will turn yellow if it is treated with strong soap during laundering.  Often the instruction for cleaning clothes contains the sentence: Use only lukewarm water for cleaning. Otherwise the quality of the product will decrease. Because natural fibers are mostly mixed with artificial ones, laundering should not be applied.  Instead of laundering, dry cleaning is applied.  To dry clean, means to use different chemical those are able to dissolve grease and stains in a similar manner as soaps, the only difference being that contact with water is avoided. 21 22