Tennant, Charles (DNB00)
TENNANT, CHARLES (1768–1838), manufacturing chemist, born on 3 May 1768 at Ochiltree, Ayrshire, was son of John Tennant by his wife Margaret McLure. He received his early education at home and afterwards at the parish school of Ochiltree. He was then sent to Kilbachan to learn the manufacture of silk, and subsequently to the bleachfield at Wellmeadow, where he studied the processes employed for bleaching fabrics. After having learned this business he set up a bleachfield at Darnly in partnership with one Cochrane of Paisley.
The old process of bleaching consisted in boiling or ‘bucking’ the cloth in weak alkali, and finally ‘crofting’ it or exposing it to the sun and air for eight to ten days on grass. At the close of the eighteenth century this second process was being gradually displaced by the use of chlorine, a substance which was discovered by the Swedish chemist Scheele, and was first applied to bleaching on the large scale by Berthollet in 1787. A solution of the gas in water was first employed, but the water was afterwards replaced by dilute potash ley, the resulting liquid being known as ‘eau de Javelle.’
In 1798 (23 Jan.) Tennant took out a patent (No. 2209) for the manufacture of a bleaching liquor by passing chlorine into a well-agitated mixture of lime and water, a strong bleaching liquor being thus obtained very cheaply. A number of Lancashire bleachers made use of the process without acknowledgment, and an action was brought against them by Tennant for infringement of patent rights (Tennant v. Slater). It was proved that the process had been secretly used near Nottingham by a bleacher who had communicated it only to his partners and to the workmen actually employed upon it. Lord Ellenborough nonsuited the plaintiff ‘on two grounds: 1. That the process had been used five or six years prior to the date of the patent. 2. That the plaintiff was not the inventor of the agitation of the lime-water, an indispensable part of the process’ (Webster, Reports of Patent Cases, i. 125; Higgins, Digest of Patent Cases, p. 87; cf. Carpmael, Reports on Patent Cases, i. 177).
Tennant was subsequently presented with a service of plate by the bleachers of Lancashire in recognition of his services to the industry. In 1799 he took out a new patent (No. 2312) for the manufacture of solid bleaching powder by the action of chlorine on slaked lime, and in 1800 removed to St. Rollox, near Glasgow, where, in partnership with Charles Mackintosh, William Cowper, and James Know, he established the well-known chemical works for the manufacture of bleaching powder and the other products of the alkali industry. His time was mainly devoted to the development of this undertaking, but he also took an active interest in the railway movement, especially in the neighbourhood of Glasgow, and was present at the opening of the Liverpool and Manchester railway. He died on 1 Oct. 1838 at his house in Abercrombie Place, Glasgow. He was the father of John Tennant of St. Rollox, whose son, Charles Tennant, created a baronet in 1885, was M.P. for the city of Glasgow from 1879 to 1880, and for Peebles and Selkirk from 1880 to 1886.[Walker's Memoirs of Distinguished Men of Science of Great Britain living in 1807–1808 (1862), p. 186 (a portrait is included in the engraving accompanying this work, taken from a picture by A. Geddes); Roscoe and Schorlemmer's Treatise on Chemistry, 1897, ii. 426.]