150th Anniversary: Death of Thomas Graham

Thomas Graham was born on December 20, 1805, in Glasgow, UK [1]. He entered the University of Glasgow in 1819 at only 14 years of age. His father had wanted him to become a pastor, but Graham developed an interest in chemistry. He studied, e.g., under Thomas Thomson, a proponent of Dalton’s atomic theory. Graham received his M.A. in Glasgow and then joined the University of Edinburgh, UK, for postgraduate studies. In 1830, he became Professor of Chemistry at Anderson’s College in Glasgow, and in 1837, he moved to take up a professorship at University College London, UK.

Graham is known for his work on the diffusion of gases. The eponymous “Graham’s law” was formulated by him in 1848. It states that the rate of diffusion or effusion (escaping from a container through a small hole) of a gas is inversely proportional to the square root of its molecular weight. Graham also studied the structures of phosphates and arsenates [2]. To this day, sodium polyphosphate is also known as “Graham’s salt.

Graham performed pioneering work on dialysis and is considered one of the founders of colloid chemistry. He investigated the diffusion of dissolved compounds through a semipermeable membrane, thereby developing chemical dialysis. Graham observed that some substances can pass quickly through such a membrane and form crystals when dried, while others only diffuse very slowly through the membrane and do not form crystals—for these, Graham coined the term “colloids” [3]. It is derived from the ancient Greek word for glue, κόλλα (kólla).

In 1828, Graham was elected a Fellow of the Royal Society of Edinburgh. In 1841, he co-founded the Chemical Society of London and became its first President. In 1854, Graham was named Master of the Royal Mint, the last person to hold this position. Thomas Graham died on September 16, 1869, in London [1].

Thomas Graham is the answer to Guess the Chemist (93).

References and Footnotes

[1] Dates according to Former Fellows of The Royal Society of Edinburgh 1783 – 2002: Biographical Index
Part One, The Royal Society of Edinburgh, 2006. ISBN: 0 902 198 84 X
An obituary in Scientific American, October 9, 1869, gives his date of birth as December 21, 1805, and Encyclopaedia Britannica gives his date of death as September 11, 1869.
[2] XIII. Researches on the arseniates, phosphates, and modifications of phosphoric acid,
Thomas Graham,
Philos. Trans. R. Soc. London 1833, 123, 253–284.
https://doi.org/10.1098/rstl.1833.0015
[3] Liquid diffusion applied to analysis,
Thomas Graham,
Philos. Trans. R. Soc. London 1861, 151, 183–224.