-6concentrated nitric acid. dried and diluted with water, then
plated on one and one-half-inch stainless steel planchets.
One-ml aliquots of the oxalate and citrate fractions were
plated directly on the planchets and dried.
The samples were
counted for beta activity in a windowless methane gas-flow
chamber.
The oxalate plates were counted after drying, after
flaming, and with a filter of 4.7 mg per cm@ aluminum in
order to identify the radiation from Fe>> (16).
The remainder of each fraction was dried and analysed
with a gamma spectrometer equipped with a two-inch,
sodium lodide crystal.
well-type,
The isotopes were identified by their
gamma energies, maximum beta energies, half lives, and elution
patterns.
Beta and gamma counts were converted to disintegrations
per minute (d/m) by the use of correction factors previously
described (16).
Disintegration rates for the individual
radioisotopes were corrected to the date of collection.
The fractions eluted from the second column (Dowex 1)
were counted in solution for gamma activity and the fractions
containing the peaks of radioactivity from mn54 , C057,60,
op
zn©5 were combined into three groups
and
(Mn,
Co, Zn), dried,
the disintegration rate of each group determined.
Radiochemical separations in duplicate for 8r90-y99 were
made on each of the five samples and their filtrates according
to the method outlined in the chemical procedures of the Health
and Safety Laboratory
(New York Operations Office) (11).