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Stability of acidified aqueous solutions of chloramine-T
Tahnta. 1965. Vol. 12. p. 1057. Pergamon Pm8 Ltd. Printed in Northem Irclattd
LETTER TO THE EDITOR
Stability of acidified aqueous solutions of cbloramine-T SIR,
I wish to report some observations on the stability of acid$ed aqueous solutions of chloramine-T, a reagent that has recently commanded some interest in titrimetric analysis.l-* Although the stability of “neutral” aqueous solutions (stock solutions) of this reagent has been extensively examined,’ no quantitative studies seem to have been carried out on the stability of the solutions in acid media. Such a study was, therefore, undertaken, especially in view of the several oxidimetric back-titration procedures which have been carried out employing &lot-amine-T in acid media. It is found that decinormal aqueous solutions of chloramine-T may be acidified with sulphuric acid (up to an overall acidity of even 3N) and may be kept in tight@stoppered vessels for periods as long as 48 hr with only slight deterioration (less than 0.3 %). In a typical experiment, when 2400 mmole of chloramine-T in a 2.7ON sulphuric acid medium was kept aside for 48 hr, the deterioration was only O-21%. When the acidified mixture is kept in open vessels, there is appreciable deterioration, especially when the atmosphere above the liquid is continually renewed by sweeping with an inert gas like carbon dioxide, making the vessel “most open”. Under the latter conditions, the deterioration on keeping 2400 mmole of chloraminsT in a 27ON sulphuric acid medium amounted to as much as 3 % in only 4 hr. When hydrochloric acid is used instead of sulphuric acid, there is appreciable decomposition even on keeping the acidified mixture in closed vessels. This relative stability of chloramine-T is in sharp contrast to the instability of hypochlorites in acid media. The present findings are explicable in terms of the equilibria existing in acidified chloramine-T solutions as discussed by Bishop and Jennings1 C. G. R. NAIR
Department of Chemistry University of Kerala Trivandrum-1 KeraIa State India. 16 August 1965
REFERENCES 1 E. Bishop and V. J. Jennings, Takznta, 1958,1,197; 1961,8,22,34,697; 1962,9,581,593,603,679. a V. R. S. Rao and A. R. V. Mm-thy, ibid.,1960,4,206. * C. G. R. Nair and A. R. V. Murthy, J. Sci. Ind. Res., India, 1961, ZlB, 147; Chem. andZnd, 1962, 1539.
1057
LETTER TO THE EDITOR
Stability of acidified aqueous solutions of cbloramine-T SIR,
I wish to report some observations on the stability of acid$ed aqueous solutions of chloramine-T, a reagent that has recently commanded some interest in titrimetric analysis.l-* Although the stability of “neutral” aqueous solutions (stock solutions) of this reagent has been extensively examined,’ no quantitative studies seem to have been carried out on the stability of the solutions in acid media. Such a study was, therefore, undertaken, especially in view of the several oxidimetric back-titration procedures which have been carried out employing &lot-amine-T in acid media. It is found that decinormal aqueous solutions of chloramine-T may be acidified with sulphuric acid (up to an overall acidity of even 3N) and may be kept in tight@stoppered vessels for periods as long as 48 hr with only slight deterioration (less than 0.3 %). In a typical experiment, when 2400 mmole of chloramine-T in a 2.7ON sulphuric acid medium was kept aside for 48 hr, the deterioration was only O-21%. When the acidified mixture is kept in open vessels, there is appreciable deterioration, especially when the atmosphere above the liquid is continually renewed by sweeping with an inert gas like carbon dioxide, making the vessel “most open”. Under the latter conditions, the deterioration on keeping 2400 mmole of chloraminsT in a 27ON sulphuric acid medium amounted to as much as 3 % in only 4 hr. When hydrochloric acid is used instead of sulphuric acid, there is appreciable decomposition even on keeping the acidified mixture in closed vessels. This relative stability of chloramine-T is in sharp contrast to the instability of hypochlorites in acid media. The present findings are explicable in terms of the equilibria existing in acidified chloramine-T solutions as discussed by Bishop and Jennings1 C. G. R. NAIR
Department of Chemistry University of Kerala Trivandrum-1 KeraIa State India. 16 August 1965
REFERENCES 1 E. Bishop and V. J. Jennings, Takznta, 1958,1,197; 1961,8,22,34,697; 1962,9,581,593,603,679. a V. R. S. Rao and A. R. V. Mm-thy, ibid.,1960,4,206. * C. G. R. Nair and A. R. V. Murthy, J. Sci. Ind. Res., India, 1961, ZlB, 147; Chem. andZnd, 1962, 1539.
1057