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The programme looks at the relationship between the discovery of groups of elements and the available technology at the time. It examines how the number of known elements has changed over the years.
Metadata describing this Open University video programme
Module code and title: S101, Science: a foundation course
Item code: S101; 12
First transmission date: 22-05-1979
Published: 1979
Rights Statement:
Restrictions on use:
Duration: 00:24:00
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Producer: David Jackson
Contributor: Charles Harding
Publisher: BBC Open University
Keyword(s): Bromine; Caesium; Calcium; Chlorine; Helium; Iodine; Potassium
Subject terms: Nitrogen; Plutonium; Sodium; Chemical elements; Chemistry, Inorganic
Footage description: Film shots of metallic copper being turned to copper oxide by the application of heat. Charlie Harding, at the reconstructed site of a bronze age village, explains how the people that produced metallic copper from malachite ore. The smelting process is demonstrated. Harding then demonstrates how metallic tin was produced from casserite ore. Finally, he explains how bronze alloy was produced from these two metals. Film shots of fuel assemblies being put into a nuclear reactor. Charlie Harding (voice over) explains that some of the known elements are man made. He goes on to look at a histogram of known elements which shows the number of these for each year from the 18th century to the present. Harding reworks an 18th century experiment which separated nitrogen from the air and also Priestly's experiment which separated oxygen gas from mercuric oxide by application of strongly focused sunlight. Using the laboratory at the Royal Institution, Harding works three experiments which were done to separate chlorine, bromine, and iodine. He then lists some properties which these elements have in common. Film shots of lead/acid batteries of the type invented by Humphrey Davy. Shots of hydrogen and chlorine being separated by electrolysis and of hydrogen and oxygen being separated by the same process. Charlie Harding explains how Humphrey Davy obtained potassium from potassium hydroxide by passing a charge through the solid alkali. Shots of the experiment being carried out. Harding goes on to demonstrate the method used by Davy to obtain calcium from calcium hydroxide through electrolysis. Charlie Harding lists, and briefly demonstrates, some of the techniques, developed in the 19th century, such as the use of blowpipes, dissolving substances in acids, selective precipitation, crystallisation, and gravimetric analysis, which allowed the next great leap in the discovery of elements. Harding deals, particularly, with the work of Kirchoff and Bunsen who studied the spectra of minerals and by this method discovered the element caesium. Harding, at the University of London Mill Hill Observatory, explains how the element helium was discovered by Lockyer through a spectroscopic analysis of the sun during an eclipse. Shots of the spectrum of helium and of the sun while he talks. Harding goes on to explain how the noble gases neon argon, krypton, and xenon were discovered in the atmosphere. The process, developed by William Ramsey involved the liquification of air and the distillation of this to separate the gases. Shots of the apparatus of the neon spectrum, and of neon lights in London.
Master spool number: 6HT/72904
Production number: FOUSC12E
Videofinder number: 1187
Available to public: no