analyzed here to perform such an analysis.
3.9
RADIOACTIVE PARTICIE SIZE ANALYSIS
The dried samples from all trays of each collector were combined,
weighed, and then sieved through a 44-91: sieve. The weight of each
fraction was determined and a weighed portion of each fraction was
used for radioautographye
These fractions were washed from the weighing dishes with
tolusne onto the backside of Eastman NTB stripping film which was previously mounted on 4-in. plastic rings. The transfer was done in dim
light. Canada balsam, which was added before the toluene evaporated
to form a uniform adhesive medium for the particles,did not interfere
with microscopic observation. The celluloid backing separated the
particles from the emulsion so that during processing the particle
medium was not disturbed (Fige 3.29).
emulsicn and a J=y thick backing.
The NTB film has a 10—p thick
The radioautogranhs were exposed for the empirically determined
time of 15 hr for samples measuring 100,000 cpm, 25 hr for samples
counting 50,000 cpm, 60 hr for 25,000 cpm, etc. All exposures were
started 6 to 9 days after each shot. The radioautographs were developed in Eastman Kodak D-19 Developer for 5 min at 20° C., then rinsed
and fixed for 10 min. All develcping operations were done without disturbing the particle medium. The particles were projected at a magnification of 1000 times with a micro-projector which consisted of a
Bausch and Lomb research microscope mounted on a micro-projector base
with carbon arc illumination. The particle images we-e pro jected at
a mgnification of 1000X. Radioactive particles cnly were measured.
The limitations of the optical microscope precluded the observation of
particles below abcut 1 pe
PARTICLES
_
BACKING
CANADA BALSAM
t
— |
eMULsion
PREPARATION POSITION
DEVELOPING
SOLUTION
EWULsion
{
BACKING '
CANADA
PARTICLES
BALSAM
DEVELOPING ANO EXAMINATION
Fige 3029
POSITION
Preparation of Particle Medium; Developing
and Examination Position of Stripping Film
85