The Romance of Modern Chemistry

ELEMENTS WITH DOUBLE IDENTITY One of the main characteristics of wood charcoal is its power of absorbing gases in large quantities, a property which renders it of value in the purification of bad air. By passage through charcoal filters sewer gases and other noxious emanations may be rendered harmless. Bone- black, again, has a remarkable power of removing colouring matter from liquids, such as red wine or indigo solution ; it is accordingly employed very extensively in decolourising sugar during the process of refining. Lamp- black, on the other hand, is applied for quite different purposes. It is useful as an artist’s pigment in both oils and water colours, and forms the chief ingredient of Indian ink and printing ink. The uses to which carbon in its various forms may be put are, in fact, legion, and in the face of these it is necessary to re-emphasise the fact that diamond, black- lead, and charcoal are all modifications of this one element. The fundamental experiments on which this statement is based were carried out more than a century ago. Before this, people were in great doubt about the exact nature of the diamond, but it was then shown that, starting with a given weight of either diamond, graphite, or char- coal, one obtained in all three cases the same weight of the gas carbon dioxide, and nothing else besides. This experiment proved incontestably that diamond, graphite, and charcoal are merely different forms of one and the same element The explanation which was given for the existence of two modifications of phosphorus is valid also in the case of carbon. Diamond, graphite, and charcoal differ, not in the number of atoms contained in the molecule, but in the arrangement of the molecules to form the substance as it appears to our eyes. 57