with Krylon. Use of nuclear emilsion striroing filn is the better technique. However, because of the unavailability of the stripping film, the majority of the work was done using the autoradiographic techniszues described above, All diameter meesurements were made on one axis cnly using an optical microscope with a micrometer eyepiece. The least count of the micrometer was 2}. . Each plate was scanned and measurements on the radioactive particles were recorded. The minimum diameter of particles measured in this analysis was of the order of 5 p. 4el.3 Particle Density FKeasurements 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 viffer ential fallout collector. Particle density was determined by a flotation methoc. with mix- tures of bromotenzene and bromoform as the liquid phase. Ina liquid system containing only two comnenents, the densities and refractive index ‘valves are an additive function of the compositions. Correspond~ ing densities and index of refraction with composition are available fron the literature. Pure bromobenzene has a density of 1.499 and an index of refraction of 1.550 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-rl glass-stoppered volumetric flask half filled with a solution of density approximating 2. Inverting the flask allowed vertical movement of the particle along the flask stem, Drops of the appropriate liquid then were added and mixed until verticsl] 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 imnlied 4 constent ratio between the measured sanple activity and the infinite gamma field at the sampling station. This imolicaticn was found to be valid only Sor the gummed paper collectors, The ratio was not constant when anplied to the total collectors. 4.2.1 Total Collectors All measurements of gamma activity were made in the 47 ionizetion chember, Annendix 2 tabulates all cata as measured, Where activity in the total collectors was found to exist in both the liquid and soli2 phases the total activity for that collector was determined by simply adding the liquid and solid phase measured values. ihe data from the land stations, after being converted to equivalent mr/hr values, were compered to the equivalent field survey deta obtained by both Task Force 46