Calcium Isotope with Mass 41 and the Radioactive Half-Period of Potassium

Abstract

CAREFUL determinations have been made of the atomic weight of calcium extracted from two very old potassium-rich deposits—one a felspar from Rhiconich, Sutherlandshire, estimated at 1,000 million years old, the other a pegmatite from Portsoy, Banffshire, probably about 600 million years old. Each mineral contained approximately 9 per cent K₂O and less than 0.3 per cent CaO, so that there seemed reasonable grounds for hope that the accumulation of the calcium isotope with mass 41, through the slow radioactive disintegration of the potassium in the deposit, might be sufficient to induce a detectable change in the atomic weight from the normal value.