Copyright © 2007 Dorling Kindersley
Materials from the chemical industry are all around us. They include chemicals to make paint for cars, plastic for computers, and PHARMACEUTICALS (medicines). Chemical engineers start with cheap, raw (natural) materials, such as PETROCHEMICALS, seawater, and minerals. They separate materials by using physical processes, such as evaporation, and by using chemical reactions. These processes take place in factories, called chemical plants.
The elements that make up salt – sodium and chlorine – are used to make paint, soap, fertilizer, detergents, and paper. Salt is collected by evaporating water from a salt solution. In hot countries, seawater is fed into wide, shallow pools called salt pans. The water evaporates in the sun, leaving salt. The salt is then transported to factories all over the world.
At huge chemical plants, in a process called electrolysis, an electric current is passed through brine (concentrated salt water). This breaks up brine into its elements (parts). Chlorine from the salt and hydrogen from the water are released. Sodium and hydroxide ions are left behind, as sodium hydroxide. This alkali is used to make soap, paper, and some pigments. Chlorine is used to make plastics, and hydrogen to make fertilizers.
Many pigments are made using sodium hydroxide. Pigments are coloured compounds (chemical mixtures) that do not dissolve in water. They are fine powders that mix easily to colour paint and printing ink. Modern pigments are made by chemists in huge plants. Pigments are often made by mixing solutions of chemicals. The mixture is filtered, dried, and crushed to a fine powder by a series of heavy rollers.
To make paints, pigments are mixed with a sticky liquid called a binder in huge vats. A chemical called a wetting agent is stirred in by a machine with rotating blades. The wetting agent makes the paint flow easily. Water-based paints use water as their wetting agent. Gloss paints use a chemical called white spirit. When an object is painted, the wetting agent evaporates and the binder hardens.
Crude oil is a sticky, dark liquid found under the ground or sea. Each drop of oil contains hundreds of hydrocarbon (hydrogen and carbon) compounds, called petrochemicals. Chemists separate the different hydrocarbons into fractions by heating them at an oil refinery. Thousands of products are made from hydrocarbons.
The pharmaceutical industry creates thousands of medicines to help prevent and fight disease. Chemists create synthetic substances in a laboratory to target specific illnesses. These substances are made artificially by heat and chemical reactions. After thorough testing, the substances are made into medicines.
A research chemist models molecules on a computer. The computer has a large database of how atoms bond and react with each other. This helps the chemist to model a molecule that has the right kind of shape and structure to interact with chemicals inside our bodies. The chemist has in-depth knowledge of a particular illness and the body chemicals involved.
Chemists combine and test thousands of molecules to create compounds for a new medicine. Chemists make and test the compounds in small amounts for three years of laboratory trials. The compounds that show promise and pass safety tests are then tested on people for five years in clinical trials.
After clinical trials, the compounds that treat an illness most successfully are developed into new medicines. Tablets or capsules are a useful way of distributing the medicine because they are easy to store and take. Some capsules have a gelatine coating that dissolves in the stomach, releasing the medicine.