Synthesis of enriched solutions of chloramine starting from hypochlorite at high chlorometric degree

The synthesis of high-grade chloramine was studied starting from sodium hyp ochlorite solutions containing 25% in NaOCl. The reagents at 100 chlorometr ic degrees are relatively stable and lose approximately 1.4 degrees by 24h at 17 degreesC. They present a temperature of crystallization of 14.2 degre esC (precipitation of NaOCl . 5H(2)O) but it is possible to use them at - 2 0 degreesC in undercooling state. To obtain quantitative yields, it is nece ssary to neutralize the totality of hydroxide ions generated by the reactio n and to operate below -10 degreesC in order to limit oxidation of chlorami ne by the hypochlorite ions. The addition of an acceptor soluble salt is th e most appropriate solution because it regenerates ammonia as soon as it is consumed and stabilizes chloramine by maintaining the pH around 10. The am moniacal combinations NH4NO3-NH4Cl-NH3-H2O and NH4NO3-NH3-H2O are compatibl e and allow to operate in monophasic medium until -30 degreesC. The yields are close to 95% with a titre in NH2Cl of 2.3 M (11.4%). Experiments carrie d out in continuous rating lead to a monochloramine solution of 2M. (C) 200 1 Elsevier Science B.V. All rights reserved.