1799 - Charles Tennant patented bleaching powder (chloride of lime); 1800 - Tennant founded a chemical works at St.Rollox, Glasgow principally to produce bleaching powder (calcium hypochlorite), which was sold worldwide. By 1815 - business was known as Charles Tennant & Co. and had expanded into other chemicals, metallurgy and explosives. St. Rollox was the largest chemical works in the world during the 1830s and 1840s, covering over 100 acres (0.4 km2) with ne thousand employees; 1842 - the chimney known as the St. Rollox Stalk aka Tennant's Stalk towered over the factory was built. 1922 - the chimney was struck by lightning and had to be demolished; Company later known as the United Alkali Company Ltd.; 1926 - merged to form Imperial Chemical Industries Limited. The chemical works at Springburn closed in 1964. The company still exists and has headquarters in Bath Street, Glasgow and a factory in Maryhill.