Radium, and other radio-active substances : polonium, actinium, and thorium. With a consideration of phosphorescent and fluorescent substances, the properties and applications of selenium, and the treatment of disease by the ultra-violet light / by William J. Hammer.

  • Hammer, William Joseph, 1858-1934.
Date:
1903
Catalogue details

Licence: In copyright

Credit: Radium, and other radio-active substances : polonium, actinium, and thorium. With a consideration of phosphorescent and fluorescent substances, the properties and applications of selenium, and the treatment of disease by the ultra-violet light / by William J. Hammer. Source: Wellcome Collection.

    18/104 (page 4)
    Phosphorescence by insolation—or exposure to sunlight—has been extensively investigated by Prof. A. E. Becquerel and Dr. John W. Draper. Practically all substances in nature are phosphorescent, and although some of them remain phosphorescent for only one ten- thousandth of a second, others retain their phosphorescence for hours. One may expose sulphide of calcium to sunlight, and after placing it in a dark room for six weeks it will still affect a photo- graph plate. Phosphorescence may be stimulated in many ways—by com- bustion, pounding, rending, friction, by the vibrations from sources of heat, light or electricity; and these various phosphor- escent substances are very susceptible to temperature changes. Various substances also phosphoresce while undergoing crys- tallization. I have here a large sheet of cardboard which has been prepared for me by Messrs. Devoe & Company, which is covered with seven coats of Balmain’s Luminous Paint or poly-sulphide of calcium, with perhaps a trace of bismuth and mixed with aerated varnish; and it has been put through hot calender rollers. You will note that this phosphoresces most beautifully when ex- cited by burning this piece of magnesium wire before it, or by focusing the arc light upon it. This phosphorescence soon dies out, however; but upon placing my hand against the sheet, the heat of my hand has caused the card to brilliantly phosphoresce. A cold object placed against the cardboard will very much lessen the phosphorescence at that point. When I place this bust of Franklin between the arc light and the phosphorescent cardboard, you will note I can thus produce a fine silhouette of that distinguished philosopher. I have prepared for your consideration a number of objects coated with phosphorescent substances. When I burn this piece of magnesium wire in front of this card, or hold it before the arc light, you will note the initials of the A. I. E. E. and the A. E. S., the two societies before which I have the honor of appearing to-night, shine out brightly. I also have a number of incandescent lamp bulbs, coated internally and exter- nally with phosphorescent substances, which you will note give considerable light when stimulated by the burning mag- nesium ; or by turning on the electricity supplying certain of the lamps. I remember nearly twenty years ago'having cut~out tiny stars