Blagden, Charles

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Blagden, Charles

(b. Wooten-under-Edge, Gloucestershire, England, 17 [?] April 1748; d. Arcueil, France, 26 March 1820)

physical chemistry.

Virtually nothing is recorded of Bladen’ family background or education. He studied medicine at Edinburgh and received the M.D. in 1768. He was elected a fellow of the Royal Society in 1772 and served as a medical officer in the British Army from about 1776 to 1780. From about 1782 to 1789 Blagden was Cavendish’ assistant. Neither man ever revealed “the circumstances which brought them together or separated them” (G. Wilson, Life of Cavendish p. 129). Cavendish settled an annuity on Blagden and left him a considerable legacy.

Blagden succeeded Paul Henry Maty as secretary of the Royal Society on 5 May 1784, at a time when the Society was sorely divided over the efficacy of the administration of its president, Sir Joseph Banks. Blagden, Banks’ close friend for many years, was elected secretary by a large majorty. Both in this capacity and as Cavendish’ assistant he became involved in the prolonged “water controversy” —the question of priority in discovering the composition of water, claimed by both Cavendish and James Watt in England and by Lavoisier in France. Blagden admitted responsibility for conveying, quite well meaningly, word of the experiments and conclusions of both Watt and Cavendish to Lavoisier; and he seems to have been careless in overlooking errors of date in the printing of Cavendish’ and Watt’ papers. There appears, however, to be little ground for the charge, leveled by Muirthead and other supporters of Watt’ claims, that Bladen deliberately falsified the evidence in favor of Cavendish.

Bladen’ earliest published papers concerned experiments carried out on himself Banks, and others, to determine the endurance of air temperatures of up to 260°F.— he found the body temperature did not rise by more than one or two degrees. He also wrote a history of the attempts by Cavendish and others to determine the freezing point of mercury. A series of experiments on the super cooling of distilled water and solutions of salts led Bladen to study the effects of dissolved substances, beginning with common salt, on the freezing point of water. His conclusion that the salt lowers the freezing point in the simple inverse ratio of the proportion the water bears to it in the solution has come to be known as Bladen’ law, although Richard Watson first discovered the relationship in 1771 (see. J.R. Partington, Text-book of Inorganic Chemistry [London 1921], p. 103; and Waston, in Philosophical Transactions61 [1771], 213–220). Nearly a century elapsed before his results could be integrated into a new theory of solutions initiated by the work of Raoul. Arrhenius, and van’t Hoff; in the meantime, Blagden’ work was virtually forgotten until Louis de Coppet drew attention to it in 1871.

Blagden spent much of his time in Europe, particularly in France— he was a close friend of Berthollet and other French scientists. Indeed, he had gone to live in Arcueil shortly before he died. He was knighted in 1792.


Original Works. Blagden published little outside the philosophical Transactions of the Royal Society. Among his papers are “Experiments in a Heated Room” in philosophical Transactions65 (1775), 111–128, 484–494; “History of the Congelation of Mercury,” ibid.,73 (1773), 329–397; “Experiments on the Cooling of Water Below Its Freezing point,” ibid., 78 (1778), 125–146; and “experiments on the Effect of Various Substances in Lowering the point of Congelation of Water” ibid., 277–312.

II. Secondary Literature. A biography is F. H. “Sir Charles Bladen,” in Osiris, 3 (1937, 69–87. The two sides of the “water controversy,” giving diametrically opposed opinions respecting Blagden’ integrity, are best studied in J.P. Muirhead ed., Correspondence of the Late James Watt on His Theory of the Composition of water… (London, 1846); and G. Wilson, The Life of the Honorable Henry Cavendish, Including Abstracts of His Most Important Scientific papers, and a Critical Inquiry Into the Claims of All the Alleged Discoverers of the Composition of Water (London, 1851). The latter gives a useful bibliography of the subject and a biographical sketch of Blagden.

E. L. Scott