CENTRAL SCIENTIFIC CO., CHICAGO, U. 8. A. 



219 



4867. 

 4868. 

 4870. 



No. 4866. 



OVENS, see general heading Ovens. 



RADIOACTIVITY APPARATUS, see general heading Radioactivity Apparatus. 



RECTIFIERS 



4866. RECTIFIER, ELECTROLYTIC, or NODON VALVE. Consists of four cells with electrodes of lead 

 and aluminum, and depends for its action on the fact that an electric current will not enter the 

 electrolyte from the aluminum electrode, but will pass freely into the electrolyte from the lead. 

 The electrodes are fastened to a substantial non-conducting top, with binding posts for both 

 A. C. and D. C. circuits. The connections are made by straps of metal, so that the path of the 

 current is readily traced. 



This valve, though not as satisfactory as a Motor Generator, may be used on either 110 or 220-volt 

 alternating circuit with a moderately high efficiency. Currents of from 5 to 8 amperes may be 

 obtained for laboratory use, and for short periods of time, much larger currents may be drawn 



from the valve. Complete with chemicals, glass jars, and full directions $19.00 



CHEMICALS for No. 4866, per complete charge 50 



GLASS JAR for Xo. 4866, for replacements 40 



RECTIFIERS, TUNGAR. These rectifiers consist of a bulb filled with an inert gas at low pres- 

 sure and having for cathode a filament of small tungsten wire coiled into a closely wound spiral 

 and for anode a piece of graphite of relatively large cross section. The tungsten filament is 

 heated to incandescence by being placed in the secondary circuit of a transformer, which is 

 part of the outfit. This incandescent filament, as is well known, emits electrons and ionizes 

 the rarified gas in the bulb, which thus becomes a conductor of electricity. In addition to be- 

 ing in the secondary circuit of the transformer, the tungsten filament is connected to one ter- 

 minal of the A. C. line and the graphite electrode to the other terminal. During the half -cycle 

 in which the filament is negative, the electrons being themselves negative are driven from the 

 filament and across to the graphite positive electrode, ionizing the gas molecules as men- 

 tioned above and permitting the passage of a current. During the other half of the 

 cycle when the filament is positive, if any electrons are emitted, they are immedi- 

 ately attracted to the filament again, so that the gas remains non-conducting. Since the direc- 

 tion of a current is opposite to the direction in which the negative electrons travel, it is evident 

 that the current passes during each alternate half -cycle from the graphite electrode to the tung- 

 sten filament through the bulb. We therefore have in the circuit of the bulb a pulsating uni- 

 directional current. 

 This current is especially adapted to battery charging but may be used for many other purposes 



such as in electrolytic experiments, electro-plating, for running small motors, etc. 

 Tungar Rectifiers are designed for 115 volt, 60-cycle circuit, but may be used on from 105 to 125 

 volt circuit. They are mounted in a black japanned casing, with a perforated top. This cas- 

 ing contains the bulb, the transformer and a fuse to protect against overloads. These rectifiers 

 are especially superior to many rectifiers or the market in that they operate satisfactorily when 

 only a fraction of their full output is being used. Nos. A and B are provided with legs for 

 placing on floor or table; No. C is intended for wall installation, and is provided with ammeter. 

 Furnished with cord and plug for attachment to any incandescent lamp socket. 



No. 



Output, full load, watts. . . . 



Amperes, full load 



Volts, full load 



Height, inches 



Depth, inches 



Width, inches 



Shipping weight, Ibs 



Each 



4871. TUNGAR BULB only, renewal. 



A 



15 



2 



7.5 

 8'4 

 5% 

 6% 



12 

 16.00 



3.00 



B 

 90 

 6 

 15 

 10 

 8 



6% 



24 



24.00 



7.00 



C 

 450 



6 

 75 

 14 

 12% 



81 



115.00 

 8.00 



