Thomas Graham was born in Glasgow, Scotland on December 21, 1805, and was the son of a prosperous manufacturer. He was educated at the University of Glasgow and then taught for seven years at nearby Anderson College. Here he carried out his first important study on the diffusion and effusion of gases, the work for which he is today best remembered. He found the same law for diffusion (through Plaster of Paris) and for effusion (through a small hole in a platinum disc), namely “that the diffusion rate is inversely as the square root of the density.” He astutely noted that “diffusion takes place between the ultimate articles of gases, and not between sensitive masses.” Today we know that under real conditions both laws are only semi-quantitatively true. Later he extended this work to the diffusion of one liquid into another, and these investigations eventually led to his division of solutes into crystalloids, such as salt and sugar, and colloids, such as gum arabic and the finely divided gold suspensions of his London colleague, Michael Faraday. This was the beginning of colloid chemistry. He developed dialysis as a means of freeing colloidal solutions from electrolytes but could not have conceived of the multifarious purposes to which that technique is now used. He also did pioneer work on the phosphates and arsenates leading to the generalized concept of polybasic acids.

In 1837 he was appointed Professor of Chemistry at University College, London, and in 1841 he was one of the prime movers and the first president of The Chemical Society of London, the world’s first. In 1855 Graham, like Isaac Newton before him, accepted the position of Master of the Mint. The post died with him in 1869.

References
DSB, Vol. V, pp. 492-495.
R. A. Smith, The Life and Works of Thomas Graham. Glasgow: Smith & Sons, 1884.

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