[en] A simple and safe procedure using the radioisotope dilution method for determining the mercury amount in electrolytic cells in the soda industry, has been investigated. The procedure developed is based on the correct supply by the Japan Atomic Energy Research Institute of the aliquots of radioactive mercury i.e. ¹⁹⁷Hg, precisely weighed and the standard reference sample accurately diluted. A high accuracy was achieved with the s.d. in the determination less than 1 %. (author)