The chemistry of ‘being in the limelight’.

In Oxford Open Learning’s distance learning Chemistry IGCSE course students learn about the production of calcium oxide, also known as quicklime. In today’s blog, one of our science tutors takes a look at the history of quicklime and limelight.

‘Being in the limelight’ is a common expression meaning being at the centre of attention, or, in the theatrical sense, being in the spotlight on stage. The phrase’s origins lie in the use of limelight as a type of stage lighting in 19^th century theatres and music halls.

If calcium carbonate, or limestone, is heated it produces calcium oxide, also called quicklime. Limelight is produced by heating quicklime to a high temperature. When it’s heated with a flame produced by burning a combination of hydrogen and oxygen gases through a blow pipe, quicklime glows a bright white, or, in other words, becomes incandescent – this is known as limelight.

Although, with the right mix of gases, a combination of oxygen and hydrogen can reach 2800°C the flame must be kept below the melting point of quicklime which is 2572°C.

The famous French scientist Antoine Lavoisier is credited as the first to blow oxygen through a blow pipe in 1782. Robert Hare (b.1769 in Willingdon, Sussex) and Edward Daniel Clarke (b.1781 in Philadelphia) experimented with the oxy-hydrogen blowpipe – oxy-hydrogen is a mixture of oxygen and hydrogen gases. Sir Goldsworthy Gurney (b.1793 near Padstow, Cornwall) developed the oxy-hydrogen blowpipe further in 1823 while at the Surrey Institute. His development resulted in a larger more stable flame than his predecessors had managed. After seeing a demonstration of the light, in 1826 Thomas Drummond (b.1797), a Scottish Civil Engineer, used it to provide light in surveying applications.

The lighting system was first used in the theatre in 1837 at Covent Garden. It was then used around the world in theatres and music halls in the 1860s and 1870s for spotlighting and creating sunlight and moonlight effects. The lights, known as Limes, were also placed at the front of the balcony for general stage illumination.

As a result of using dangerous gases and flames for limelight, there were numerous theatre fires during this time. The Royal Alhambra Theatre in London had a major fire in 1882 in which a wall collapsed nearly killing the Prince of Wales. In 1885, The Theatre Royal in Exeter burnt down while still using limelight, and 278 people died as a result of a fire caused by a stage light at the Brooklyn Theatre in New York in 1876. Such incidents lead to improved safety regulations including the use of a metal fire curtain to divide the theatre from the auditorium in the event of a fire. Numbers of fire exits were also increased, walls were made stronger to prevent collapse, and water supplies were improved for fire fighting.

The fire risk, together with the fact that each light needed its own operator to keep adjusting the oxygen and hydrogen gas cylinders and the position of the quicklime, meant that in the late 19^th century the Limes were replaced by electric lights . But ‘being in the limelight’ has persisted as a common saying.

Andrew Bateson

Tutor

IGCSE Chemistry home study students cover the topic Acids, Alkalis and Salts, including work on calcium carbonate, as part of their Physical Chemistry work. Oxford Open Learning’s home learning students also look at the use of limestone in the extraction of iron ore.

For more information on Oxford Open Learning’s IGCSE Chemistry course contact a student adviser on 0800 9757575.