A glow in the dark Ancient elements It was difficult to do complex experiments thousands of years ago In those days philosophers thought carefully about the world and came up with ideas to explain what they saw Aristotle was a Greek philosopher who was born in 384 B C E He thought that everything on Earth was made from four elements These were air earth fire and water Aristotle could not prove this but people thought highly of him so his ideas influenced science for almost 2,000 years This began to change in the 17th century Unlucky for some Just 13 elements were known in the 1660s These included nonmetals such as carbon and sulfur and metals such as gold copper and iron But because everybody still believed in Aristotle’s idea of four elements no one recognized these substances for what they were true elements Alchemy In 1669 German alchemist Hennig Brand tried to make gold from urine Instead he discovered the element phosphorus Alchemy was a strange mixture of chemistry religion and mystery One of its aims was to make gold from cheaper substances As Brand thought Urine is golden colored so it might contain gold This 1771 painting by Joseph Wright shows an alchemist making phosphorus 10
Red phosphorus is a form of phosphorus that catches fire at a higher temperature than white phosphorus It is used in matches Bringer of light Brand collected fifty buckets of urine He left them to stand for several days and then heated the stinky sludge to concentrate it He heated the remaining ghastly goo to evaporate some of it and then cooled the vapor In this way Brand used distillation to collect a pure waxy white solid Once in the air this gave off a green glow in the dark and it could suddenly burst into flames It was called phosphorus after the Greek words meaning bringer of light Brand had discovered that phosphorus is an element found naturally in the body Our bones contain most of it and any extra comes out in our urine THAT’S A FACT Brand was lucky Had he collected his phosphorus in the open air instead of water he could have been seriously hurt White phosphorus does not react with water but it is very dangerous in air It can set itself on fire and then burn violently Today it is used in incendiary bombs which cause damage by starting fires Breakthrough Brand never made his fortune from his discovery Even though he tried to keep his methods secret other people worked out how to make phosphorus and became rich Brand’s discovery of phosphorus encouraged the search for other new elements There was a good chance that if a new element could be found through experiments others could also be found 11
The skeptical chemist Candles and mice Around the same time as Brand’s discovery of phosphorus John Mayow was experimenting with air He published his results in 1668 In one experiment Mayow put a lighted candle in a dish of water and covered it with an upturned jar The flame eventually went out and water rose a little inside the jar If he put a mouse inside instead of a candle it eventually suffocated and water rose again Mayow then discovered that a mouse would suffocate faster if there was a lighted candle in the jar as well Mayow’s experiments do not sound very pleasant but he had made two important discoveries He had discovered that flames and living things need the same part of air Since only some of the air was John Mayow published some of his results in 1674 These diagrams showed readers how his experiments on air were set up 12
Robert Boyle Date of birth January 25 1627 Place of birth Lismore Ireland Greatest achievement Boyle’s book was a turning point in chemistry His experiments on gas pressure and volume led to Boyle’s law of gases Interesting fact In 1680 Boyle turned down the chance to be the president of the Royal Society the world’s oldest scientific organization Date of death December 31 1691 used up and not all of it he discovered that air must contain at least two different gases It could not be an element after all Doubts about Aristotle’s four elements were starting to grow Toward modern elements Robert Boyle published a book called The Sceptical Chymist in 1661 He discussed THAT’S A FACT Mayow and Boyle were at Oxford University at the same time and it is possible that Mayow did his experiments in Boyle’s laboratory Robert Hooke a scientist who had once been Boyle’s assistant helped Mayow become a Fellow of the Royal Society the chemical ideas of his day including those of Aristotle Boyle noted that blood broke down when heated forming more than just four substances On the other hand gold would not break down at all By the time the second edition of the book was published in 1680 Boyle had worked out how to make phosphorus himself and he had carried out many experiments on air Boyle defined an element as a substance that cannot be broken down He argued that only experiments could show if a substance was an element Breakthrough Boyle provided the first modern definition of an element He argued that the ancient idea of four elements was wrong and that experiments are needed to show if a substance is an element 13
