Toxicity and Permeability: I. The Toxicity of Acid and Basic Solutions of Sodium Arsenite to Mosquito Pupae1

Abstract

The relative toxicity to mosquito pupae of dilute acid and basic solutions of sodium arsenite have been studied by determining the lengths of immersion required to cause fifty per cent mortality. Over the range of concentration 0.01 molal to 0.03 molal, the acidic solutions (pH 5) are approximately four and one-half times as rapid in their toxic action as the basic solutions (pH 11). The results are discussed in terms of the adsorption mechanism of toxic action and it is suggested that adsorption is important chiefly because it is a step in the penetration of toxic substances. The greater toxicity of acidic solutions of sodium arsenite is attributed to the greater ease of penetration of tissues by the arsenious acid molecules of the acid solutions as contrasted with the difficulty of penetration by the sodium arsenite ions of the basic solutions.