METHODS
Preparation of Plates
Preparation of plates was the same as described in WT-616
(UWFL-33):18.
Briefly,
the wet or moist samples were placed on
weighed 1 1/2-inch (1 5/8 inch over-all) stainless steel plates,
weighed,
550°C,
dried overnight at 97° -99°C,
and finally reweighed.
cover the plate smoothly,
reweighed,
ashed overnight at
The ash was slurried with alcohol to
dried and affixed with a few drops of 0 5
per cent Formvar in ethylene dichloride.
Storage
Plates were stored on 2 1/2 x 3 1/4-inch cards perforated
Reade
with a1 1/2-inch hole into which the plates fitted.
The cards
bearing the plates were stored in wooden boxes with tall,
slotted compartments,
narrow,
so that 25 cards bearing plates could be in-
serted in each tier,
totalling 100 plates to the box.
of ash to the plate,
care in handling,
Firm fixation
and occasional inspection
of
the cards for evidence of spill guarded against loss or contamination
of ash.
However two decay curves had to be excluded,
more curve was discontinued,
and one
on account of loss or contamination.
Counting
In addition to the description of counting methods given in
WT-616 it may be said that a special 1 1/2-inch-thick lead shield