. Light energy, its physics, physiological action and therapeutic applications . rods, c c. The glasstube a is smeared over with a conducting coating of phos-phoric acid, and the whole system hangs from the stopper, d,of the glass bulb, /. Strips of tin foil, c e, at the sides of thebulb are connected to earth. As long as there is air in thebulb no divergence of the leaves is observed, since the ladiumrays make this air a conductor. But if a good vacuum bemade in the vessel, the leaves soon begin to diverge, owingto the loss of negative electricity by the radium. This diver-gence increases unt
. Light energy, its physics, physiological action and therapeutic applications . rods, c c. The glasstube a is smeared over with a conducting coating of phos-phoric acid, and the whole system hangs from the stopper, d,of the glass bulb, /. Strips of tin foil, c e, at the sides of thebulb are connected to earth. As long as there is air in thebulb no divergence of the leaves is observed, since the ladiumrays make this air a conductor. But if a good vacuum bemade in the vessel, the leaves soon begin to diverge, owingto the loss of negative electricity by the radium. This diver-gence increases until the leaves touch the tin-foil this happens the leaves are discharged and collapse,and the cycle recommences. With a weak radium prepara-tion, Strutt obtained a full divergence in about 20 with a more active preparation the cycle can be com- TLlec. World and Engineer, April 9, 1904. 704 LIGHT ENERGY. pleted in course of a lecture. The time in which the cycle iscompleted is, of course, an indication of the degree of radio-activity of the substance in Fig. 43.—Apparatus for Demonstrating the Absorption of theRadium Radiations. Strutt. A Modification of Strutts Apparatus Demonstrating theNegative Charge of the |3 Radiations.—Paschen,1 in anillustrated note, shows that the apparatus of Strutt fordemonstrating the positive charge of radium enclosed in aglass tube, may be modified so as to demonstrate also thenegative charge of the (3 radiation which penetrates the shown in the illustration, a glass bottle which may beevacuated contains the small glass tube b, which contains aradium-barium preparation, and is suspended by means ofthe quartz rod, a. Two quartz tubes, ax and a±, hold the hol-low lead vessel c, of a thickness of 2 mm., which is com- ^hys. Zeit., March 15, and Elec. World and Eng., April 9, 1904. KAIHUM. 705 pletely insulated from b. Through b passes in spiral form theplatinum wire, f, which is connected to the electroscope,
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