METHOD FOR MEASURING SULFUROUS ACID

PURPOSE:To obtain an analytical value correlating with a ventilating distillation method for both wine and fruit juice without necessitating a troublesome operation such as distillation, by adding an L-cysteic-acid-added salt to a sample before addition of alkali to the sample. CONSTITUTION:A sample introduced from a sample injector 15 is put in a reaction tank 20 by a pump 19. With a selector valve 17 operated, then, an L-cysteic-acid-added salt water solution is put in the reaction tank 20 from a reagent injector 16 by the pump 19. Lastly, an alkaline solution 18 is put in the reaction tank 20 by operating the selector valve 17. The concentration of L-cysteic-acid-added salt to be added is 0.017 to 1.67W/V% preferably for the whole sample solution constituted of the sample to be tested, the L-cysteic- acid-added salt water solution and the alkaline water solution. The sample subjected to the alkaline treatment is sent to a mixer 21 and mixed with an acid buffer solution 22 added by a pump 23. The sample thus mixed is sent to a reaction tank 25 kept at a prescribed temperature by a thermostat 24 and a change in a potential is measured by a microorganism-immobilizing oxygen electrode or a pH electrode 26.