Question

38. Chloropicrin, also known as PS and nitrochloroform, is a chemical compound currently used as a broad-spectrum antimicrobial, fungicide, herbicide, insecticide, and nematicide. In World War I, the Germans used it as tear gas since it is also an airway irritant. This substance is a liq- uid at room temperatures. Suppose there was a small spill of this material on a paved surface at a chemical plant. The spill has a width of 0.8 ft and a length of 2.5 ft. The prevailing wind is 10 miles per hour in a direction parallel to the length of the spilled material. Estimate the rate of evaporation in grams per hour of this material. Chloropicrin has a diffusivity in air of 0.088 cm2 s−1. At 25°C, its vapor pressure is such that its equilibrium concentration in air would be equal to 0.211 g L−1. The kinematic viscosity of air under these conditions is 0.157 cm2 s−1. Carefully state your assumptions.

Answer 1

This question has been solved by using mass transfer analogy. Average Mass Transfer Coefficient over the entire length has been calculated by using the analogy based on Calculating Heat Transfer Coefficient over the entire length. Length of the spill has been assumed to be 'Characteristic length' because the wind is flowing parallel to the length of the spilled material.