This system has a background of about 50 counts per minute
and an efficiency of approximately 38 per cent based on p32,
The counts
for biological samples were converted to disinte-
grations per minute per gram (d/m/g) of wet tissue and the
counts
for samples of island soil and beach sand were con-
verted to d/m/g of dry material at time of counting by applying correction factors for sample weight,
counter efficiency,
and self-absorption.
The values for gross beta
activity in the
appendix
tables are given in d/m/g plus or minus the 95 per cent
counting
error, which was obtained from nomographs based on
the ratio of the counting rate and total time of counting of
the gample to the counting rate and total time of counting
of background (Kinsman, 1957).
The values in the summary
tables, Tables 2 and 3, however, have been calculated in
terms of micromicrocuries per gram
(\ic/g)
of wet tissue.
The samples collected in 1958 were analyzed for gammaemitting isotopes with a 3 x 3-inch sodium iodide crystal
connected to a Radiation Counter Laboratory 256<-channel ana~
lyzer.
The radioisotopes present in the samples were identi-
fied by their gamma energies and for some of the samples the
by a subtractive
Sy
amount of each radioisotope was determined