Industrial Chemistry – NDA Chemistry Notes

The buildings around you are made of cement. The windows are made of glass. The notebooks you write in are made of paper. The medicines you take are made in chemical plants. All of these involve industrial chemistry.

This chapter covers six main industrial products: cement, glass, paper, fertilisers, gunpowder, and paints. Questions from this chapter are mostly direct fact-based questions about raw materials, processes, and uses.

The chapter is straightforward. Know the raw materials, the key processes, and the specific facts that examiners repeat.

1. Cement

Cement is the material that holds bricks together. When you add water to cement and it hardens, that is a chemical process called setting.

Raw Materials for Cement: The two most important raw materials for making cement are limestone and clay. Gypsum is also added later. [NDA 2012-I] The most important raw material for cement is limestone. [NDA 2011-I] The main ingredient in cement is limestone.

Manufacture of Portland Cement: Step 1: Limestone (CaCO₃) and clay are crushed and mixed in the right proportions. Step 2: The mixture is heated in a rotary kiln to about 1400-1500°C. Step 3: At this high temperature, the limestone decomposes and reacts with clay to form a hard ball-like material called clinker. Step 4: Clinker is cooled and ground into fine powder. Step 5: Gypsum (CaSO₄·2H₂O) is added to the clinker during grinding.

Why is Gypsum Added? Gypsum is added to clinker during cement manufacturing to decrease the rate of setting of cement. Without gypsum, cement would set too quickly. Workers would not get enough time to mix, pour, and shape the cement before it hardens. Gypsum acts as a retarder. It slows down the setting process.

Composition of Portland Cement: Portland cement is mainly composed of calcium silicates and calcium aluminates. The components in decreasing order of quantity are:

CaO (lime) > SiO₂ (silica) > Al₂O₃ (alumina) > Fe₂O₃ (ferric oxide) [NDA 2012-I]

Approximate percentage: CaO = 60-70% | SiO₂ = 20-25% | Al₂O₃ = 5-10% | Fe₂O₃ = 2-3%. A substance with this approximate composition is Portland cement. [NDA 2012-II]

Setting of Cement: When water is added to cement, the calcium silicates and calcium aluminates undergo hydration. They combine with water to form complex hydrated products. This process is called setting.

Setting of cement is an exothermic process. It releases heat. This is why concrete structures have to be cooled by spraying water during setting. If the heat is not removed, the concrete can crack.

Cement is a mixture, not a compound. [NDA 2009-II] It contains calcium silicates and calcium aluminates but in variable proportions. Limestone is used in the cement industry.

2. Glass

Glass is all around you. Windows, bottles, spectacles, mirrors, all are made of glass.

What is Glass? Glass is a supercooled liquid. It has infinite viscosity at room temperature. It is an amorphous solid. It has no regular crystal structure. [NDA 2011-I] Glass is a man-made silicate. Its major component is silica (SiO₂). [NDA 2011-II] Glass is NOT a crystalline substance. [NDA 2011-I]

Because glass is a supercooled liquid, very old windows (centuries old) are slightly thicker at the bottom than at the top. The glass has very slowly flowed downward over hundreds of years.

Glass does not have a fixed melting point. [NDA 2006-I] This is because glass is amorphous. It gradually softens over a range of temperatures rather than melting sharply at one temperature.

Manufacture of Soda Lime Glass (Common Glass): Soda lime glass is the most common type of glass. It is used in windows, bottles, and ordinary glassware. Raw materials: Silica (SiO₂) + Sodium carbonate (Na₂CO₃) + Calcium carbonate (CaCO₃). These are heated together in a furnace to form glass. The major constituent of soda lime glass is silica. [NDA 2012-I, NDA 2011-II]

Type of Glass	Key Component Added	Special Property	Use
Soda lime glass	Na₂CO₃ + CaCO₃	Common, cheap	Windows, bottles
Borosilicate glass (Pyrex)	Boron oxide (B₂O₃)	Heat resistant, low expansion	Laboratory glassware, cooking
Flint glass	Lead oxide (PbO)	High refractive index	Lenses, spectacles, crystal
Optical glass	Special purity silica	Very clear, precise	Telescopes, cameras
Coloured glass	Metallic oxides	Specific colours	Decorative, signal lights

Coloured Glass: Different metallic oxides give different colours to glass. [NDA 2011-II]

Metallic Oxide Added	Colour Imparted to Glass
Uranium oxide	Yellow/green
Cuprous oxide (Cu₂O)	Red
Cobalt oxide (CoO)	Blue
Chromium oxide (Cr₂O₃)	Green
Manganese dioxide (MnO₂)	Violet/purple
Iron oxide	Green or brown

Occupational Hazard (Silicosis): Workers in ceramics, pottery, and glass industries breathe in fine silica dust over many years. This causes a serious lung disease called silicosis. Silicosis damages and scars the lung tissue. It reduces the ability to breathe. There is no cure.

Glass Wool: Glass wool is made from fine glass fibres. It is used as an insulating material. Glass wool is fireproof and is used to prepare fibre glass. It does NOT have high electrical conductivity.

3. Paper

Every page you read is made of paper. Paper is made from plant fibres.

Raw Material for Paper: The main raw material for paper is cellulose fibre. Wood, bamboo, sugarcane bagasse, and rags all contain cellulose. [NDA 2009-I]

What is Bagasse? Bagasse is the fibrous residue left over after sugarcane juice has been extracted from sugarcane. It is a by-product of the sugar industry. Bagasse is used for the production of paper.

Manufacture of Paper: Step 1: Wood or other cellulose-containing raw material is chipped into small pieces. Step 2: The chips are treated with chemicals to break down lignin and release cellulose fibres. This step is called degumming or pulping. Degumming of raw material in paper manufacturing is done using caustic soda (NaOH). Step 3: The cellulose pulp is washed and bleached using bleaching powder or chlorine. Step 4: The pulp is diluted with water and spread on a wire mesh. Water drains away. Fibres bond together. The sheet is dried. Step 5: The dry sheet is pressed and rolled to make paper.

Bleaching powder is used to bleach paper pulp.

4. Fertilisers

Plants need nitrogen, phosphorus, and potassium (NPK) to grow. Fertilisers supply these nutrients. Fertilisers are either natural (organic) or synthetic (inorganic).

Types of Fertilisers: Vermicompost is an organic biofertiliser. It is made from decomposed organic waste using earthworms.  Inorganic fertilisers provide macronutrients: nitrogen, phosphorus, and potassium.

Nitrogen Fertilisers: Urea (CO(NH₂)₂), ammonium nitrate (NH₄NO₃), ammonium sulphate ((NH₄)₂SO₄). Urea has the highest nitrogen content (46.7%) among common fertilisers. [NDA 2009-I]

Phosphate Fertilisers: Superphosphate: made by treating rock phosphate with sulphuric acid. Metal present in superphosphate is calcium. [NDA 2010-I], Superphosphate is soluble in water and can be absorbed by plants. Rock phosphate is insoluble and cannot be directly used by plants.

Nitric Acid in Fertiliser Industry: Nitric acid is used in the production of ammonium nitrate fertiliser.

5. Gunpowder (Black Powder)

Gunpowder is one of the oldest known explosives. It was invented in China and brought to Europe in the Middle Ages.

Composition of Gunpowder: Potassium nitrate (KNO₃) = 75% + Charcoal (C) = 15% + Sulphur (S) = 10%. Potassium nitrate is also called saltpetre. It is the oxidising agent. It provides oxygen to support rapid combustion. Charcoal provides the fuel. Sulphur lowers the ignition temperature. [NDA 2013-II]

Gases evolved during explosion: N₂: CO₂ = 1: 3 [NDA 2011-II]

Cellulose nitrate (gun cotton) is used to make gunpowder. [NDA 2012-I], Cellulose nitrate → gun powder]

Modern Explosives:

Explosive	Chemical Name	Notes
Dynamite	Nitroglycerin absorbed in kieselguhr	Invented by Alfred Nobel
TNT	Trinitrotoluene (C₇H₅N₃O₆)	Military explosive
RDX	Research Department Explosive	Powerful military explosive
Nitroglycerin	Glyceryl trinitrate	Also used as medicine for heart conditions

Alfred Nobel invented dynamite and used the profits from his invention to establish the Nobel Prizes. Sulphuric acid is used in the production of explosives.

6. Paints

Paint is what you put on walls and furniture to colour and protect the surface. A paint consists of three main components.

Components of Paint: Pigment: the colouring agent. It gives the paint its colour and hiding power. Vehicle (Binder): an oil or resin that holds the pigment together and sticks it to the surface. Linseed oil is a common vehicle. Solvent (Thinner): a liquid like turpentine that makes the paint easy to apply. It evaporates after painting.

White Pigments:

Pigment	Chemical Name	Notes
White lead	Basic lead carbonate 2PbCO₃·Pb(OH)₂	Old type, now largely banned due to lead toxicity
Zinc white	Zinc oxide (ZnO)	Non-toxic, used for interior walls
Titanium white	Titanium dioxide (TiO₂)	Brightest white, most common today

Coloured Pigments:

Metallic Oxide / Compound	Colour of Paint
Chromium oxide (Cr₂O₃)	Green
Iron oxide (Fe₂O₃)	Red (red ochre)
Cobalt blue	Blue
Carbon black	Black
Cadmium yellow	Yellow

Chromium oxide makes the colour of paint green.