1026 



Voltaic Electricity. Section 9: Electron Theory and Radioactivity. 



No. 63 159 



63 159. 



63163. 



63 163. 



63168. 1 : 1. 



63.159. Vacuum Tube after Perrin, for demonstrating the negative charge produced by 

 cathode rays, Figure, on base 



63.160. Glow Lamp for the Edison Effect, Figure 



The electrons issuing from the incandescent carbon loop give a negative charge to an insulated 

 aluminium sheet contained in the same. A sensitive galvanoscope between aluminium sheet and posi- 

 tive pole of the lamp, gives a deflection, while showing no current between aluminium sheet and 

 negative lead of lamp. 



63.161. Glass Plate with covering, for the Hall Effect 



Apparate for Opto-electrical Experiments. 



63.162. Zinc Disc, amalgamated, with insulating holder, with terminal 



The zinc disc is connected with a sensitive electrometer by a thin wire. If the electrometer 

 be negatively charged, a quick discharge occurs when the zinc disc is brilliantly lighted by an elec- 

 tric arc lamp, or, better still, by a mercury vapour lamp made of glass permeable to ultra-violet 

 rays (Uviol Lamp No. 63,198). When the electrometer is positively charged no discharge occurs on 

 illumination. The uncharged electrometer becomes positively charged when the illumination is applied. 

 The first two experiments can be carried out with a sensitive leaf electroscope (e. g., 60,176, 60,186, 

 60,196, 60,202); a sensitive electrometer (e. g., quadrant electrometer No. 60,720) is necessary for the 

 third experiment. The zinc disc must be freshly amalgamated before use. 



When ultra-violet light is allowed to fall upon a spark gap connected up to an induction coil 

 it is bridged over at a considerable distance, as without the action of light (cf. Gratz, Die Elektrizi- 

 tat, 15th Edn., p. 348). 



A transparent gypsum slab does not effect the discharge much, while a glass plate annuls it, 

 since the action chiefly depends on the ultra-violet light. 



63.198. Uviol Mercury Vapour Lamp with Stand, for connecting to 65 220 volts D. C. . 



63.163. Potassium Cell after Elster & Geitel, Figure (Wied. Ann. d. Phys., 1894, Vol. 

 52, p. 433) 



The cell also acts with white light and gives an opto -electrical current. It is placed in a dar- 

 kened box and put in series with a very sensitive mirror galvanometer of high resistance and with 

 a 100 200 volt battery, the tension being regulated in such manner that no current overflows at 

 the cell. The surface of the potassium metal is connected to the negative pole and a wire-shaped 

 aluminium electrode with a positive pole. If the surface of the potassium is lighted by sunlight or 

 a sufficiently strong source of light, a passage of the current takes place in the cell, the intensity 

 of which is proportional to the strength of the light. 



63.164. Sodium Cell for the same experiment 



63.165. Potassium-Sodium Amalgamating Cell 



63.166. Sodium Cell with Quartz Window 



63.199. Sodium-Amalgam Cell for opto-electrical discharge by daylight (cf. Gratz, Die Elek- 

 trizitat, 15"' Edn., Fig. 337) 



Radioactivity. 



63,167. Radium Cell, F i g u r e, without charge 



The radium cell consists of an ebonite chamber containing on one side a small flat cavity fur 

 the radium bromide charge. A mica plate secured by a metal cover having a hole in the middle, 

 closes the cell off on this side. The active rays of the radium bromide can issue at this open side 

 of the cell through the mica plate, the back of the cell acting as a screen. 



Radium Bromide for above quoted for on application. 



For tilling the cell ."> to In milligramme radium bromide are employed. 



s. d. 

 1.10.0 

 1.14.0 



0. 4.0 



0. 5.0 



5.10.0 

 2. 0.0 



1. 15.0 

 3. 0.0 

 3. 0.0 



1. 2. 



0. 3.0 



Cl. 1965, 



6510,5277,3821.1966 



