In October 1838, Charles Tennant died and his son John Tennant (1796-1878) became general manager of the company. In 1890, the general decline of the company caused by the transfer to the Solvay process which was externally patented, led the company to merge with many other chemical manufacturers in the UK to form the United Alkali Company but it continued to trade as Charles Tennant & Co. In 1913 the company was incorporated as Charles Tennant & Co Ltd.

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