NITEATES FROM ATMOSPHERE — SCOTT. 



363 



along the positive electrode than along the negative, as shown in 

 figure 3. » _t ^ 





Fig. 3. 



"^^'lien the flame 

 is burning it emits 

 a loud noise, from 

 which the furnace 

 attendant can 

 judge of the num- 

 ber of arcs formed 

 per second. The 

 electrodes are 

 changed and re- "J" 

 paired every 300 

 hours, and the fire- 

 proof lining every 

 fourth to sixth 

 month. The temperature of the flame is about 3,500° C, and the 

 temperature of the escaping gases is between 800° and 1,000°. 



estflac Each of the furnaces at Notodden takes 600 kilo- 



watts, and the fiu'naces at the Rjukan works each 

 take 3,000 kilowatts. 



SCHONHERR FURNACE. 



This furnace was invented by Dr. Schonherr, of 

 the Badische Anilin imd Soda Fabrik of Germany. 

 As installed at Christiansand, it consists of a long 

 iron tube fixed vertically, through the center of 

 which an arc 16 feet long is maintained. Alter- 

 nating current at 4,200 volts, 50 periods, is used, 

 and each furnace takes 600 horsepower. A.\y blown 

 through this tube with a whirling motion keeps the 

 arc in the center. The electrode at the bottom 

 consists of an iron rod which passes through a 

 copper water-cooled tube. The iron rod is pushed 

 upwards, as it burns away to ferric oxide, and fresh 

 rods are screwed on as required, so that the process 

 does not stop. At the top of the tube there is a 

 water cooler, and it is inside here that the arc ends 

 by striking across from the center to the side of the 

 tube. 



As will* be seen from the arrows in figure 4, the 



incoming air passes through annular tubes, on each 



side of which there are the hot gases from the 



air is thus heated to about 500° C. before it 



After passing through the arc, where some of it 



Fig. 4. 



furnace. The 

 reaches the arc. 



