LEAD SULFIDE.233 RADIUM

The experiment conducted by Rutherford and his co-workers involved bombarding gold foil with alpha particles, which are doubly charged helium atoms. The apparatus used in their experiment is shown in Figure 14-9. The alpha particles are produced by the radioactive decay of radium, and a narrow beam of these particles emerges from a deep hole in a block of lead. The beam of particles is directed at a thin metal foil, approximately 10,000 atoms thick. The alpha particles are delected by the light they produce when they collide with scintilltaion screens, which are zinc sulfide-covered plates much like the front of the picture tube in a television set. The screen... 

Chemically related to barium, radium is recovered from its ores by addition of barium salt, followed by treatment as fur recovery of barium, usually as the sulfate. The sulfates of barium and of radium are insoluble in most chemicals, so they arc transformed into carbonate or sulfide, both of which are readily soluble in HC1. Separation from barium is accomplished by fractional crystallization of the chlorides (or bromides, or hydroxides). Dry, concentrated radium salts are preserved in sealed glass tubes, which are periodically opened by experienced workers to relieve the pressure, The glass tubes are kept m lead shields,... 

Other salts of somewhat more Interest to the radlo-chemlst which exhibit the same type of behavior are barium carbonate, barium sulfate, radium sulfate, radium chloride, radium sulfate (H5), lanthanum carbonate, barium chloride, silver chromate (W4) and. barium nitrate (h6). Mercury (ll) sulfide, although not studied In sufficient detail to warrant classification Is reported to carry lead under a variety of conditions (12). Copreclpltatlon of lead with mercury (II) sulfide Is especially useful since the mercury can be removed subsequently by sublimation. This Is accomplished by dissolving the mixed lead and... 

The nature of the experiment is indicated by the drawing in Figure 3-11. A piece of radium emits alpha particles in all directions. A narrow hole in a lead block defines a beam of the alpha particles. This beam of alpha particles then passes through the metal foil, and the directions in which the alpha particles continue to move are observed. The direction in which an alpha particle moves can be detected by use of a screen coated with zinc sulfide. When an alpha particle strikes the screen a flash of light is sent out. 

Barium sulfate, BaS04 Calcium sulfate, CaS04 Lead(II) sulfate, PbS04 Radium sulfate, RaS04 Silver sulfate, Ag2S04 Strontium sulfate, SrS04 Sulfides... 

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