THOMAS, SIDNEY GILCHRIST

(b. London, England, 16 April 1850; d. Paris, France, I February 1885)

metallurgy.

Thomas invented and commercialized the basic process for dephosphorizing pig iron in the making of wrought iron and steel. As a result of his work, vast deposits of phosphoric iron ores that were previously unsuitable could be converted into steel by either the Bessemer or open-hearth methods. By the early years of the twentieth century most steel was being made by the basic process.

Thomas’father, William Thomas, was a Welshman employed in the civil service. Between the ages of ten and sixteen Thomas was educated at Dulwich College (equivalent to a high school or preparatory school), where he prepared for the matriculation examinations at London University. He intended to study medicine. When his father died in 1867 he abandoned these plans, and after a brief tenure as a teacher of classics at an Essex school he accepted a junior clerkship at a London police court. The following year (1868) he voluntarily transferred to the Thames police court in Stepney, the lower depths of London society, and he remained there for eleven years until the success of his invention enabled him to devote himself completely to metallurgy.

In a full account of his life, his sister Lilian Gilchrist Thompson reported that their mother was a “keen Liberal” and Thomas a “militant Radical” as an adolescent. He was strongly sympathetic to the North in the American Civil War, and he aspired to earn a fortune through applied science and to use it to assist the unfortunate and the neglected. Upon his early death, at the age of thirty-four, he left a sizable estate to his sister with instructions that it be used for “doing good discriminatingly”. Lilian Thompson outlived her brother by more than half a century and executed his will scrupulously, largely by sponsoring various efforts to improve the conditions of workers, especially women.

Although Thomas never married, his letters reveal a spirited appreciation of feminine companionship.

During his early years as a police-court clerk, Thomson pursued his interests in metallurgy and applied chemistry by attending courses at the Royal school of Mines and the Birkbeck Literary and Scientific Institution (now Birkbeck College). At the School of Mines he passed all of the examinations, but could not matriculate because he was unable to meet the requirement of regular attendacne at the metallurgy lectures. It was in response to a chance remark by a Birkbeck lecturer that Thomas resolved to find a method for producing Bessemer steel from phosphoric ores, a challenge that had been confounding the foremost metallurgists since the introduction of Bessemer’s process.(In the older puddling process the phosphorus was readily removed). By the end of 1875 Thomas had formulated the theory that, in order to remove the phosphorus, it was necessary to provide a strong base so that the phosphoric acid produced in the converter could combine with the base and form a slag. At first he experimented with basic linings for the converter formed chiefly of lime or limestone, but it was found that to preserve the linings from rapid deterioration and to produce a highly basic slag it was necessary to add substantial amounts of basic substances to the molten iron. In the commercial process it was mainly the additives rather than the linings that produced the phosphorus-bearing slag.

To overcome the constraints of both the demands of his clerkship and his lack of adequate experimental facilities, Thomas enlisted the collaboration of his cousin. Percy Carlyle Gilchrist, who was employed as a chemist in a Welsh iron works. The collaboration proved fruitful and in 1877 the first of many patents was taken out. Although Thomas announced his achievement the following year at a meeting of the Iron and Steel Institute, it was not until 1879 that success was achieved on a commercial scale. At the spring meeting of the Iron and Steel Institute the Thomas-Gilchrist process was fully acknowledged.

So successfully did Thomas manage his patents, and so knowledgeable was he of the intricacies of international patent law, that he was able to defend his rights against formidable challenges. One challenge was, however, irresistible. Unknown to Thomas, the British metallurgist George James Snelus had patented the use of basic linings for the Bessemer converter in 1872. Although Snelus had failed to perfect the process, or even to produce usable linings, Thomas chose to avoid litigation, and a settlement was reached through the arbitration of William Thomson (later Lord Kelvin). Snelus received a share of the profits of the British and American (but not the Continental) rights and in 1883 both men received a Bessemer Gold Medal from the Iron and Steel Institute.

During the final years of his life, Thomas took out several patents on the preparation of the phosphate-rich basic slag for use as fertilizer, a technique that achieved considerable importance after his death.

These later years were also spent in a vain search for health as Thomas traveled extensively, hoping to benefit from climates more congenial than that of Great Britain. He died after a lingering illness diagnosed as emphysema, an ailment disproportionately common among employees of the poorly ventilated London police courts.

BIBLIOGRAPHY

I. Original Works. Thomas and Gilchrist jointly authored “On the Elimination of Phosphorus”, in Journal of the Iron and Steel Institute, 14–15 (1879), 120–134: “A Note on Current Dephosphorising Practice” ibid., 19 (1881), 407–412; “The manufacture of Steel and Ingot-iron from Phosphoric Pig-iron”, in Journal of the Society of Arts, 30 (1882), 648–660. For a list of Thomas’lesser publications, see Lilian Gilchrist (Thomas) Thompson, Sidney Gilchirst Thomas: An invention and Its Consequences(London, 1940), 567ndash;57.

II. Secondary Literature.Two full biographies are R.W. Burnie,Memoir and Letters of Sidney Gilchrist Thomas(London, 1891); and Lilian Gilchrist Thompson, op. cit. The latter is based heavily on the former but contains additional material on the adoption of the basic process and on his sister’s use of the fortune he left. For biographical essays on Thomas and Snelus. see Willim T. Jeans, The Creators of the Age of Steel (New York, 1884).

Harold Dorn