The positron emitting Na22 of 2.6 year half-life has been prepared in a nuclear reactor by the double reaction Li6(n, α)H3, Ne20(H3, n)Na22. The over-all yield was 2.3 × 10−7 atoms of Na22 per atom of tritium formed. Eleven grams of lithium as aluminum alloy turnings in a neon atmosphere at 200 p.s.i. was irradiated for 175 days in a neutron flux of about 4 × 1012 n./cm.2/sec. About 380 μc. of Na22 was obtained in a sodium extract having a specific activity of 10 mc. Na22/gm. of Na23. A specific activity in the curie/gm. level would be expected from a longer irradiation in the highest flux (6 × 1013 n./cm.2/sec.) in the NRX reactor. The separation and purification of the sodium proved practicable by paper chromatography or ion exchange; the analyses for trace Li and Na23 were carried out by radioactivation.

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