In 1892, Castler, an American chemical technician living in the United Kingdom, proposed using mercury as a cathode to electrolyze salt water to produce sodium hydroxide, and obtained a patent.
On the mercury electrode, sodium ions (Na) are easier to discharge than hydrogen ions (H), and after obtaining electrons, metallic sodium is generated. It combines with mercury to form sodium amalgam. This alloy is introduced into the sodium dissolving chamber to generate sodium hydroxide and hydrogen gas.
In this way, a separator layer is no longer needed in the electrolytic cell, and the sodium hydroxide solution obtained has a higher concentration.
However, this method was taken one step ahead by the Austrian chemical engineer Keller. He patented this method before Castler. The two chemists were willing to cooperate and did not intend to litigate. In 1895, they cooperated to establish the Castler-Kerler Alkali Making Company. They were built in Niagara Falls, United States, and Runcorn, Cheshire, England, respectively, in 1896 and 1897. The factory started production. Niagara Falls has a large supply of electricity. Runcorn is adjacent to the Irish Sea in the north and has an abundant supply of salt. By 1898, the Runcorn City factory was producing 20 tons of sodium hydroxide and 40 tons of bleaching powder per day (bleaching powder was made by absorbing chlorine gas from slaked lime).