Berkeley, Randal Mowbray Thomas (Rawdon), eighth Earl of Berkeley 1865-1942, scientist, was born at Ixelles, Brussels, 30 January 1865, the only son of George Lennox Rawdon Berkeley, by his wife, Cécile, daughter of Edward Drummond (Viscomte de Melfort, in France) and divorced wife of Sir F. B. R. Pellew [qv.]. He assumed the courtesy title of Viscount Dursley from 1882 (when his father took the title of seventh Earl of Berkeley) until his father's death in 1888; in 1891 his right to the peerage was established.
Berkeley was educated in France until he came to England to be coached for the Royal Navy, joining the Britannia in 1878. As a young officer he showed great promise and was outstanding among his contemporaries, but his high spirits made naval discipline irksome and he was often in trouble. However, it was his interest in science and mathematics and his determination to do research which decided him to resign his commission in 1887. He then worked for a short time at chemistry at South Kensington, but after a serious illness he bought a house at Foxcombe just outside Oxford and began research in the Christ Church and Balliol laboratories on crystal structure and the electrolysis of glass. In 1898 he built a laboratory at Foxcombe and began to plan the researches on osmotic pressure for which his name will always be remembered. His ultimate objective was the application of van der Waal's equation of state of gases to substances in solution and for this a knowledge of osmotic pressure was necessary. It was a difficult field, as semi-permeable membranes had to be made capable of standing pressures up to 150 atmospheres, but Berkeley had an instinct for engineering design, and a genius for devising and perfecting new experimental methods. In 1902 he was joined by Ernald Hartley who was associated with him in most of his osmotic pressure work.
Few osmotic pressures can be measured directly, so Berkeley's first objective was to check the accuracy of the values found by the indirect method based on vapour pressure measurements by measuring directly the osmotic pressures of the same solutions. In spite of improvements in the vapour pressure technique the results of the two methods still showed considerable differences. Berkeley then examined the equation due to Arrhenius on which this indirect method was based, and he introduced into it an important correction. This started his interest in thermodynamics, in which he became a great adept particularly in cyclic processes applied to solutions. Meanwhile, following his lead, Alfred William Porter had derived a more exact form of the Arrhenius equation and in 1907 Berkeley invited Charles Vandeleur Burton, a physicist from the Cambridge Scientific Instrument Company, to join him in work on the compressibilities which were now involved and on other osmotic problems.
With the advent of Burton the theoretical field was extended and a joint paper Contribution to the Osmotic Theory of Solutions (Philosophical Magazine, April 1909) broke fresh ground, to be followed by Berkeley's most daring venture, a paper on Solubility and Supersolubility from the Osmotic Standpoint (ibid., August 1912). As the scope of attack widened, the Foxcombe team was enlarged to meet the growing programme of experimental research, which included diffusion and the stratification of centrifuged solutions. From 1910 to 1914 Berkeley had a well-balanced group of young physical chemists working under his stimulating leadership. Those were the great days of the Foxcombe laboratory. Much of the work was left unfinished when the team dispersed to war work and Berkeley was left to gather up the threads of the osmotic pressure work which he had pursued with such tenacity and refinement of method. The table summarizing his final results showed a very close agreement between the values of the osmotic pressures determined by the direct and indirect methods. It established, finally, the validity of the vapour pressure method and was a fine ending to his research in this most exacting field. Berkeley, however, was never satisfied and was always striving more and more for perfection. Work continued at Foxcombe until 1928 on further refinements and on its extension to non-aqueous solvents.
On the death of his kinsman, Lord Fitzhardinge, in 1916, Berkeley succeeded to the Berkeley estates. The castle was in a sad state of disrepair, and he threw himself, as his own architect and clerk of works, into its restoration with the same enthusiasm and energy which had marked his scientific work. One of his ancestral responsibilities was the mastership of the Berkeley hounds, and he took to hunting when over fifty years of age with his usual pluck and dash and was generally up to hounds. But he never lost his interest in osmotic pressure and osmotic phenomena. Long after the Foxcombe laboratory was closed he was constantly seeking new equations with physical significance to express his experimental results.
Berkeley married in 1887 Kate, daughter of William Brand, a landed proprietor, and widow of Arthur Jackson, a composer and teacher of harmony and composition at the Royal Academy of Music. She died in 1898 and in 1924 he married Mary Emlen Lloyd, daughter of John Lowell, of Boston, Massachusetts. He died at Berkeley Castle, 15 January 1942. There were no children by either marriage and the earldom of Berkeley ended with him. A fine portrait by Sir William Orpen is at Berkeley Castle commemorating Berkeley's rare combination of F.R.S. (1908) and M.F.H.
Sir Harold Hartley in Obituary Notices of Fellows of the Royal Society, No. 11, November 1942
Contributor: Harold Hartley.