[The formation of iodate as a reason for the decrease of efficiency of iodine containing disinfectants (author's transl)].

Methods are given to calculate the iodate equilibrium concentrations in aqueous solutions of iodine, containing additional iodide as well as the reaction times concerning the transformation of iodine to iodate. Using the results, which have been obtained evaluating in this manner solutions of triiodide (CI2 = CI- = 10(-6)--10(-1) M/l) as well as 0.03 M iodine solutions containing varying amounts of iodide (0--0.12 M/l) the following conclusions concerning the stability of iodine containing disinfecting agents can be made; 1. Below pH 6 a decrease of the disinfecting effectiveness owing to the formation of iodate can be excluded. 2. Above pH 7 the formation of iodate, whose extent depends extremely on the pH-value as well as the iodide concentration, has to be regarded very carefully. Raising the pH-value lowers the stability (iodate formation increases) while raising the iodide concentration improves the stability (iodate formation is reduced). 3. Because of the stabilizing effect of the iodide ion, provided that its concentration is high enough, the opposite effect of the pH-value can be overcompensated and as a result of this iodine containing agents can exhibit a stability sufficient for practice also in the weak alkaline range (pH less than 9).