Some Observations on the Germicidal Efficiency of Chloramine-T and Calcium Hypochlorite

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Abstract
A technique is described for studying the effect of temp., conc. and reaction of Cl solns. on the germicidal efficiency of Cl compounds against spores of Bacillus metiens. For chloramine-T a rise of 10[degree]C effected a reduction of about 82% in the killing time at an initial reaction of pH 6.0 and 71.5% at an initial reaction of pH 8.7. Doubling the concn. of the chloramine-T, at a given initial reaction and constant temp., reduced the killing time about 40-60%. The pH range was from 6.0 to 8.8; increasing the acidity reduced the killing time. Available Cl was not found to be a direct measure of the germicidal efficiency of Ca hypochlorite or chloramine-T. The reaction was found to be a far more potent factor than the available Cl as respects effect on germicidal efficiency. A hypochlorite solution containing 1000 p.p.m. available Cl at a reaction of pH 11.3 required 64 min. to destroy 90% of the exposed bacterial spores; the same compound diluted to 20 p.p.m. available Cl and the reaction changed to pH 8.3 required 5 min. for the same bactericidal effect.

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