DMT samples, free of the filter after sublimation, were
leached directly in water, and filtered through the hydrosol type MP
filter for the insoluble residue fraction. The filtrate was electrodialyzed for the colloidal and ionic fractions. Results of these meagurements appear in Table 4.1.
The various fractions reported above do not refer to the
state of the active aerosol as it existed in the field, as all filter
samples were of course in the solid state when received at the Labora-
tory.
The purpose was to determine if any significant amount of activity
were associated with colloidal particles in the aerosol,
{ndicate a negative conclusion,
+
4e1.2.6
The results
2:
ft
A number of shallow trays containing a thin layer of salicylic
acid crystals were placed on the floors of test compartments in the
ships YAC 39 and YAG 40. The active material settling out on the crystal
bed was transferred with the crystals to a small container, where the
salicylic acid was sublimed off, resulting in a concentrated sample.
The distribution of activity with respect to specific gravity
was determined by counting the precipitate following successive centri-
fugations of the sample in bromobenzene-bromoform mixtures of increasing
density. Results appear in Table 4.2
It should be emphasized that these measurements apply only to
that portion of the radioactive fallout and aerosol material which reached
the ships, penetrated a curtain of exhaust smoke (and washdown spray, in
some cases), entered the vent system, traversed some 50 ft of duct, and
settled to the compartment floor.
It is possible, if not probable, that
the modal specific gravity of~ 2.0 is due to carbon (Sp. gr. =» 1.8 to
2.25) and oil droplets acting aa carriers.
perticulerly black and oily in appearance,
4.2
PROP
OF F
The Shot 5 sample was
SHOT
The flour-tray drop sampling instruments23/were designed to sazple
liquid fallout over the size range of natural raindrops.
Trays of flour
(exposed area « 14 sq in) were serially exposed to the fallout, liquid
drops forming pellets in the flour and solid particles retaining their
identity. The flour trays were shipped to USNRDL, the flour sieved,
weighed, counted, and in some cases, thin-sectioned. In the event of
mixed liquid-solid fallout, the presumption was that the drop-formed flour
pellets could be easily distinguished from solid fallout material by
means of a water-soluble dye (in powder form) mixed with the flour.
Water produced pellets would then be distinctively colored, in contrast
to solid fallout particles which would retain their natural appearance
or at most be coated with the dry, white, flour-dye mixture,
93