by John Read

The elements combine together in a practically unlimited number of ways, determined by their valencies and chemical nature, to form molecules of many grades of complexity, ranging from hydrogen molecules, H2, with two like atoms, to molecules built up of various kinds and numbers of atoms. It was realised in due course that of all these distinct forms of matter (substances, or chemical compounds) which gradually became known, some occurred in lifeless mineral matter, while others were invariably found in association with living, or "organised" matter. A distinction was thus recognised in the eighteenth century, between inorganic and organic substances. Thus arose the two great divisions of this science known as INORGANIC CHEMISTRY and ORGANIC CHEMISTRY.

Among the great variety of inorganic materials are, for example, the gases of the atmosphere, waters, rocks, minerals metals and their oxides and salts, non-metals and their compounds, such as sulphuric and hydrochloric acids, and so forth. Natural organic materials include plant and animal fats, carbohydrates, proteins, dyestuffs, alkaloids, perfumes, alcohol, organic acids, rubber, coal, petroleum, and so on, in almost endless variety. A glance at such lists is sufficient to indicate that all the great manufacturing industries, including agriculture, the oldest industry of all, depend upon these two great branches of chemistry. It is evident also that the raw materials of the world can be applied economically to industrial purposes only by the application of systematic chemical methods. Inorganic chemistry is linked closely to geology, mineralogy, and metallurgy; organic chemistry to physiology, biochemistry, and biology in general. Early in the nineteenth century it was realised that all the so-called natural organic compounds contain carbon as a constituent element. At the present day many of the natural organic compounds have been synthesised by artificial processes. Moreover, thousands of artificial carbon compounds unknown in nature have been produced. Organic chemistry embraces all these compounds, so that now organic chemistry is the chemistry of the carbon compounds. Inorganic chemistry embraces all the others.

(from What is Science?, Gollancz)