UNCLASSIFIED eames en ome See ee De be evaluated. Physical observation could detail the state of the material as it landed at the station. Chemical treatment would allow the separation and measurement of soluble salts and seawater-insoluble ones which were to be defined as "insoluble solids." Radiological evaluation would assess the particle radioactivity. These experimental values then would define the physical state of the particles, particle size, density, particle spe- cific activity, total activity, and’mass of fallout per unit area. Assessment of Physical Properties Visual observations made in the shielded laboratory confirmed the slurry droplet nature of the fallout. Crystalline materials were observed to be suspended in the liquid portion of the droplets.. The characteristic cubic shape of sodium chloride was detected. After the dissolution of soluble halides, an insoluble-solids component remained on the film. It was apparent that the slurry droplets contained three major constituents: water, Soluble sea salts, and insoluble solids from the environmental materials (Fig. 1). MeasurementofHalideContent The reagent film for particle halide analysis utilized a commercial gelatin film in whichcolloidal red silver dichromate was precipitated by a special method,! Soluble halides deposited on the film were later dissolved by saturated hot water vapor and diffused into the gel structure where they were precipitated as silver salts. A microscope measure- ment of the reaction area yielded, by calibration, the weight of halides reported as sodium chloride, The yneasurable range of sodium chloride by this method is from 10" to 10% Be Measurementof Content Water When a droplet strikes the reagent film it spreads to a certain con- stant degree related to the volume of water in the droplet, 5 Insoluble solids within each fallout slurry droplet outlined this maximum spread on the collecting film. A calibration curve was constructed giving the volume of water in a slurry droplet as a function of the area cevered by the insoluble-solids trace, This area has been termed the "slurry artifact.'"' The smallest water volume measurable by this technique is about 107! ¢c¢, 2a