with Krylon. technique. Use of nuclear emulsion striroing filn is the better However, because of the unavailability of the stripping film, the majority of the work was done using the autoradiographic techniques described above. All diameter measurements were made on one axis enly using an optical microscope with a micrometer eyepiece. The least count of the micrometer was 2h. Each plate was scanned and measurements on the radioactive particles were recorded. The minimum diameter of varticles measured in this analysis was of the order of 5 p.. 401.3 Particle Density Measurements An optical microscope having a calibrated micrometer eyepiece was used to measure particle diameters along 2 axes. Relative activities were deternined wit! a gamma scintillation counter under conditions identical to those used in counting the gross samples from the Jviffer ential fallout collector. Particle density was determined by a flotation methoc. with mixtures of bromobenzene and bromoform as the liquid phase. Ina liquid system containing only two components, the densities and refractive index valves are an additive function of the compositions. Corresponding densities and index of refraction with composition are available from the literature. Pure bromobenzene has a density of 1.499 ané an index of refraction of 1.5460 while pure bromoform has a density of 2.290 and an index of refraction of 1.598. Each particle was pleced in a precision l-ml glass-stoppered volumetric flask half filled with a solution of density approximating 2. Inverting the flack allowed vertical movement of the particle along the flask stem. Drops of the appropriate liquid then were added and mixed until vertical movement of the particle ceased, indicating that the densities of the liquid and particle were identical. an Abbe refractometer was used to determine the index of refraction of the resulting liquid and hence its density from the known relationshins. 4.2 DATA REDUCTION Equation 2.1 implied a constent ratio between the measured sanple activity and the infinite gamma field at the sampling station. This implication was found to he valid only for the gummed paper collectors. ‘The ratio was not constant when anplied to the total collectors, 4e2el Total Collectors All measurements of gamma activity were made in the 47 ionize- tion chamber, Anvendix B tabulates all data as measured. Where activity in the total collectors was found to exist in both the liquid and solic phases the total activity for that collector was determined by simply adding the liquid and solid phase measured values.. she data from the land stations, after being converted to equivalent mr/hr values, were compered to the equivalent field survey data obtained by both Task Force 46