The Action of Sunlight on Sodium Pentachlorophenate

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  • Division of Biologics Standards, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland


Irradiation of dilute aqueous solutions of sodium pentachlorophenate (NaPCP) with light in the wavelength range of 290 to 330 mµ causes a chemical alteration of the NaPCP with a concomitant loss of molluscicidal activity. The reaction follows first-order kinetics, and the velocity constant is directly proportional to light intensity.

When NaPCP is used to treat the water of shallow ponds or streams exposed to bright sunlight, photochemical degradation of this agent may be an important variable, especially when the water is clear and free of solutes which interfere with light penetration.