Hydrogen engineering

Das Knallgas is oxyhydrogen, and its first half needs no explaining: der Knall is the bang a mixture of hydrogen and oxygen gives when a flame reaches it, the one German school laboratories stage with a test tube held upside down. The second half has the stranger history. Gas is not an old word at all. The Flemish physician Jan Baptista van Helmont made it up in the seventeenth century for the invisible substances he drove out of burning charcoal and fermenting wine, and he wrote himself that he had shaped it on the Greek chaos, the formless void of the old cosmologies. In his Dutch the letter g stands for much the sound German writes as ch, which is how chaos could turn into gas without anyone hearing a change. German, English and most other European languages took the word over from him ready-made, so every compound in -gas on this page, from das Knallgas to das Erdgas in the example sentences, carries one man’s invention inside it.