Boron, in the form of borax - sodium tetraborate - was known to the ancients, who used it to manufacture medicines and borosilicate glasses. The Egyptians also employed it in the process of mummification. It was not until 1808, however, that boron, in an impure state, was isolated by the scientists, Sir Humphry Davy, Louis Jacques Thenard and Joseph Louis Gay-Lussac; and it was only in 1892 that Henri Moissan succeeded in producing boron of a high purity.
The aluminium compound, alum, like borax, was known in the ancient world, where it was used medicinally to check bleeding. Sir Humphry Davy tried and failed to isolate the metal itself, but was responsible for the naming of the element, calling it 'aluminum', from the Latin word, {Ialumen}, meaning 'bitter salt'. Most countries now use the name, 'aluminium', although the USA retains the original spelling. The Danish chemist, Hans Christian Oersted, first isolated the metal in 1809.
Gallium was one of the elements predicted by the great Russian chemist, Dmitri Mendeleyev, who referred to the undiscovered metal as eka-aluminium, believing that its properties would be similar to those of aluminium. When the element was discovered spectroscopically by Paul Emile Lecoq de Boisbaudran in 1875, Mendeleyev's predictions were shown to be strikingly accurate. His figure for the density of eka-aluminium, for example, was 5.9 grams per cubic centimetre, compared with the actual figure of 5.907.
Like gallium, indium and thallium were discovered spectroscopically, and were named according to the colour of their dominant spectral line. Indium derives from the Latin word, {Iindicum}, meaning 'indigo', and thallium from the Greek word, {Ithallos}, meaning 'green bud'. Both were discovered in the early 1860s; indium by the German chemists, Ferdinand Reich and Hieronymous Theodore Richter, and thallium by the British chemist, Sir William Crookes.
