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Thomas Graham lived from 21 December 1805 to 16 September 1869. He was an eminent chemist remembered in the name of "Graham's Law", which relates to the diffusion of gases. The wider picture in Scotland at the time is set out in our Historical Timeline.

Thomas Graham was born in Glasgow. His father was a successful textile manufacturer who wanted his son to become a minister in the Church of Scotland. Graham became a student at the University of Glasgow in 1819, still aged only 14. While there, Graham developed an interest in chemistry and, despite his father's wishes, went on to study it full time, being awarded an M.A. in 1826. He then worked at the University of Edinburgh for two years before returning to Glasgow to teach chemistry and mathematics. In 1830 he became a professor of chemistry at Anderson's Institution (later the University of Strathclyde) in Glasgow.

In 1834, Graham was elected to be a Fellow of the Royal Society and in 1837 he became professor of chemistry at University College, London, a post he was to hold until 1854. In 1841 he helped to found the Chemical Society of London and became its first president. By the mid 1840s, Graham was acknowledged as the leading British chemist of his day. In 1854 he was appointed Master of the Mint (a post once occupied by Isaac Newton) remaining in post until his death in 1869.

Thomas Graham did much to develop what would now be regarded as the field of physical chemistry, and a book he wrote, Elements of Chemistry, became the standard textbook for students in Britain, as well as in many parts of Europe and beyond. Today he is perhaps best remembered for "Graham's Law" which states that the rate of diffusion of a gas is inversely proportional to the square root of its molecular weight. Graham's law provided a basis for separating isotopes by diffusion, something that later found use in many different areas of science.

Meanwhile, his study of colloids, a type of mixture where one substance is dispersed evenly throughout another, led to his invention of a machine to separate colloids and crystalloids, which he called a "dialyzer". This was the direct ancestor of the dialysis machines that are today so important to medical science. Graham's interest ranged widely. He also made contributions in areas as diverse as the determination of the formulae of different phosphoric acids; detection of the adulteration of coffee; the production of alcohol during bread-making; and the absorption of hydrogen gas by palladium metal, something that had a direct bearing on the scientific controversy caused in the 1990s by claims that energy could be produced by "cold fusion".

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