UNCLASSIFIED Measurement of Insoluble-Solids Content No known chemical method can measure the weight or volumeof insoluble solids in a deposited slurry fallout particle, Therefore, a method for comparing the volume of the fallout particle with standard volumes was developed. Five standard volumes ranging from 1077 to 1079 cc were used for the visual comparison in the microscope. They were formed by aspirating and collecting on reagent film small slurry droplets from measured aluminum oxide suspensions. The water content of each droplet was measured by its slurry artifact. By arithmetic proportion the approximate volume of aluminum oxide was known. Five appropriately sized aluminum oxide artifacts were mounted on a microscope slide as a comparison standard. Each fallout slurry artifact was then visually compared with the standards, and estimates made of the volume of insoluble solids. The physical-chemical composition of the fallout insoluble solids component is being investigated at this laboratory. Measurement of Radiological Properties After solution and diffusion of the soluble halides into the reagent film, autoradiographs were made by adaptations of the LaRiviere-Ichiki method.® These studies showed the activity to be primarily centered in the insoluble=solids portion of the fallout particle (Fig. 2). These solids were subjected to salt water leaching by the liquid phase of the droplet for at least part of their falling period. Ionic activity available for solution dissolved in this solvent. Upon striking the film the dissolved activity diffused with the water into the gelatin and there -was rigidly held, It was felt that if the active solids portion of fallout could be stripped from the film and both parts counted, a rough estimate of easily soluble ionic activity could be made. One Flathead film sample containing myriads of fallout impressions was selected for stripping and counting. The insoluble solids on the reagent film were thoroughly leached in hot water vapor at 70°C for several hours allowing further diffusion of ionic activity into the film. While the gelatin of the reagent film was still tacky from the vapor treatment, a thick layer of transparent acrylic spray was applied and allowed todry. The assemblage was then soaked in distilled water for an hour to permit diffusing moisture to loosen the solids from the gel. The acrylic film was then stripped from the gelatin, removing most of the insoluble solids with it. This stripping process was repeated until no microscopically visible insoluble solids remained on the reagent film. The commercial gelatin of the film is so tightly bound to its substrate o5—= UNCLASSIFIED KE £©& £€ E F&F g# E£E fF F FE £2 EL 2k uw kk YF ff