Images Dated 14th September 2004

Dhaka School Prize Day

Children and teachers pose for the camera during prize-giving at a school Dhaka (Dacca), Bangladesh, circa 1900. (Photo by Hulton Archive/Getty Images)

© 2004 Getty Images

15611, 2080, 5 4, 51303378, 99205, Asia, Box, Child, Diry, Education, Female, Format, Group, H Edu Scho Asia, J82140901, Landscape, Male

Rust treatment

Rust treatment. Brush being used to apply a rust removing mix of chemicals to a rusty spanner. Many commercial mixes of chemicals are available to remove rust (iron oxide). Most of them use strong acids, so skin contact should be avoided. If left, the acids will also corrode the original metal, so the chemicals should be washed off soon after use. If the rust has only affected the surface, the appearance of the original metal can be restored. However, if the rust has deeply corroded the metal, then scars and pits will be left in the metal. The use of an oil or wax coating will help prevent future cases of rusting

© ANDREW LAMBERT PHOTOGRAPHY/SCIENCE PHOTO LIBRARY

Period 3 elements

Period 3 elements. From left (in their periodic table order) they are: sodium (Na); magnesium (Mg); aluminium (Al); silicon (Si); phosphorus (P, white/red); sulphur (S); chlorine (Cl); and argon (Ar). Successive elements across the period, have a single electron added, and this causes immense changes in the chemical and physical properties. Metals (Na/Mg/Al) become non-metals (P/S/Cl/Ar), solids become gases, and reactive elements (Na/Mg) become inert (Ar). Mg is used in flares, Ar in light bulbs, and Si in microchips. P ands have different structural forms (allotropes). Cl and Ar form diatomic (Cl2) and monatomic (Ar) molecules

© ANDREW LAMBERT PHOTOGRAPHY/SCIENCE PHOTO LIBRARY