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Graham, Thomas,1805–69, Scottish chemist, best known for research in diffusiondiffusion,
in chemistry, the spontaneous migration of substances from regions where their concentration is high to regions where their concentration is low. Diffusion is important in many life processes.
..... Click the link for more information. in both gases and liquids that led to his formulation of Graham's law. His discovery that certain substances (e.g., glue, gelatin, starch) pass through a membrane more slowly than others (inorganic salts, e.g., common salt, or sodium chloride) led him to draw a distinction between the two groups, calling the former (the slower) colloids and the latter crystalloids. In this connection he discovered dialysis. His work was the earliest in colloidal chemistry. His investigation of phosphoric acid led to the present chemical concept of polybasic acids.
Born Dec. 20, 1805, in Glasgow; died Sept. 11, 1869, in London. British chemist; one of the founders of colloid chemistry.
From 1837 to 1855, Graham was a professor at University College, London, and later director of the mint. In 1836 he was made a fellow of the Royal Society. Graham was one of the founders of the London Chemical Society, and he was elected its first president in 1841. In 1829, Graham discovered the law that the rate of diffusion of a gas is inversely proportional to the square root of its density. In 1833 he disproved, on the basis of the three forms of phosphoric acid (ortho, pyro, and meta), the view that all acids are monobasic. He established the presence of internal friction in gases (1846–49). In 1861 he showed that, according to their capacity to diffuse through a parchment membrane (dialysis), all substances fall into one of two classes—crystalloids or colloids.