[Aqueous chloramine T solutions as disinfectants: chemical composition, reactivity and toxicity]

In aqueous solutions of Chloramine T (CAT), caused by dissociation, hydrolysis and disproportionation processes, seven different kinds of molecules emerge (HOCl, OCl-, R-NCl-, R-NHCl, R-NCl2, R-NH2, and R-NH- [R = CH3-C6H4-SO2]). Their equilibrium concentrations have been calculated using an iteration process (polynom of 4th degree) as a function of cCAT (0.003-10%) and pH (0-14): The (absol.) concentration of "free chlorine" ([HOCl] + [OCl-]) is surprisingly low showing a maximum concentration of HOCl in the whole concentration and pH range of only 2 . 10(-7) moles/l (0.014 ppm). The relative equilibrium concentrations of the N-chlorinated toluene sulfonamide species R-NCl-, R-NHCl, and R-NCl2, virtually alone responsible for the oxidizing and by this also disinfecting properties, owing to the extremely low concentration of free chlorine, are influenced in the concentration range relevant for practice (greater than 0.1%) only by the pH-value: At pH greater than 7 the whole oxidation capacity is present as R-NCl- (pH 7: 99.6%; pH 8: 99.96%), while at pH less than 3 it is formed by R-NHCl and R-NCl2.(ABSTRACT TRUNCATED AT 250 WORDS)