All About Inventions and Discoveries
The Romance of modern scientific and mechanical Achievements

276 All About Inventions in this manner an aggregate of 30,000 horse-power for the generation of electricity was secured. As is well known, waterfalls are numerous in Norway. The initial triumph at Notodden so favour- ably impressed the commercial world that other plants were laid down with all speed. It seemed as if every stretch of tumbling water would be taken over to furnish electricity for the production of nitrates from the air. The outstanding feature was the low cost of the current obtained in this way. At Notodden it was about one-fortieth of a penny per unit, which was less than one-half of that set down by Sir William Crookes as being necessary to secure commercial success. The process is very simple. The air blown into the furnace passes through the electric flame, the temperature of which is estimated to be about 3,000°. The nitric oxide is then driven out of the furnace. The effect of the electric flame upon the atmosphere is strikingly shown because the burned air as it emerges is heavily impregnated with the orange- coloured nitrous fumes. When leaving the furnace the burned air is extremely hot, being between 5000 and 750°. The first process is to cool it, after which it passes through a series of granite towers, in each of which streams of water are constantly trickling down. The water absorbs the nitrous fumes, thereby forming nitric acid, the strength of which increases as it passes from one tower to the other. The liquid finally flows into large granite tanks charged with limestone and caustic lime, which become saturated with the acid, thereby producing nitrate of lime. Finally, the nitrated lime is packed for market in suitable receptacles.