Water as an Activator of Luminescence

Abstract

IN the course of recent investigations on luminescence, it was noticed that many white salts showed, when wet, a bright blue luminescence under stimulation with a mercury vapour lamp, through a Uviol glass screen which excludes the visible region. On drying the salts completely, the luminescence disappears so that it appears to be due to the presence of water. The phenomenon is very widespread, being noticeable with almost any white salt. It is not confined to those salts which are appreciably soluble in water; silica, for example, showing the effect to a marked degree (this possibly accounts for the blue triboluminescence seen, for example, at the heels of a runner on wet sands at night).