On the Possible Radioactivity of Erbium, Potassium and Rubidium
McClennan and others indicate that potassium and probably rubidium is radioactive. McClennan and Kennedy' have studied various potassium, sodium, lithium, rubidium, cz;sium and ammonium salts and find that only potassium salts are appreciably active, the cz.sium and rubidium salts giving but a very slight indication of radioactivity. The potassium cyanide salts investigated by them showed an activity roughly proportional to the potassium content (the potassium content was very small in some of
... y small in some of the samples called potassium cyanide). Levin and Ruerm find by the photographic method that potassium salts emit radiations that are about a thousandth as effective in making a photographic impression as the P radiations from uranium. They find that metallic lead affects a photographic plate about as much as the potassium salts. In work upon the radioactivity of ordinary substances the electrical method is sensitive and rapid but requires a great deal of attention. The photographic method requires but slight attention and long periods of time. For these reasons the photographic method has been used by the writer in making a preliminary examination of the possible radioactivity of a large number of salts. The effects upon the photographic plate may be due sometimes to chemical action as well as to radioactive emanations or radiations. But by the use of screens it is possible in many cases to decide between these two causes. When there is no photographic impression after a long exposure of at least six months it is certain that the substance does not emit any P-like radiations as strong as the radiations from most potassium salts. Several years before his death Professor Rowland collected several minerals and salts of the rarer elements and through the kindness Phil. Nag. , No. 93 p. 377, ?908. 'Phys. Zeit. , No. 8, P. 248, zgo8.