the calcium as the oxalate and then the titrimetric determination of the oxalate with potassium permanganate, The surfcce water shots vaporized the 250 ton steel barges uponn which the devices were detonated, The concentration of iron was measured iri the fallout from these shcts by a colorimetric determinaetion of the intense red complex formed by ferrous ion and o-phenan- throline, 16/ 3.4.6 Autoradiography Portions of size-graded sample fractions were studied avtoradiographically. Each fraction was. monitored to estimate its radio‘activity, then deposited on Nuclear Track Bete stripping film and exposed for a time estimated to give good contrast between radioactivity-affected film areas and background areas, The developed autoradiograph was exanined by micronrojection to measure the particles and determine it they vere radioactive. This yielded gross size distribution, radioactive to total particle ratio, and where their number was statistically sufficient, radioactive particles size dis~ tribution, The per cent active particle data were calculated on a volume hasis: —_ % Active = (2 ny ay? active x 100 ( 2.5> “ve = dy)? mi di total The detailed technique is described in the report of Project 27 SECRET — RESTRICTED DATA