46 



THE POPULAR SCIENCE MONTHLY 



Fig. 10. RJUKAN-Fos Uppee Powee House. " The water is brought down in ten 

 pipes, each unit to furnish 14,000 horse-power." 



nitrogen and oxygen combine to form nitric oxid. This unites directly 

 with more oxygen forming nitrogen dioxid, which when dissolved in 

 water gives a mixture of nitric and nitrous acids. A very high tem- 

 perature is necessary to cause the first union of nitrogen and oxygen, 

 and at this temperature equilibrium is established wlien less than two 

 per cent, of the nitrogen is oxidized. At a somewhat lower tempera- 

 ture the nitric oxid is decomposed into nitrogen and oxygen, so that it 

 is no simple matter to cool this nitric oxid from the temperature at 

 which it is formed, without having it completely decomposed in the 

 process. This has, however, now been successfully accomplished at 

 Notodden, where I was given an opportunity of inspecting the plant. 

 A peculiar form of electric furnace is used, in which a flaming arc is 

 driven back and forth along copper electrodes by electro-magnets. 

 Through this arc air is blown, and in its passage a small proportion is 

 converted into nitric oxid. It passes so quickly that very little of that 

 which has been formed is decomposed, but on the contrary it is by tlie 

 excess of air present converted into the dioxid. 



The gases coming from the furnaces are cooled by passing through 

 pipes in boilers, and thus incidentally furnish more steam than is 

 needed for the whole plant, completely eliminating the item of coal, 

 usually such an important part of the cost of manufacture in all in- 

 dustrial plants. The gases are then passed up large towers filled with 

 broken quartz, down which water trickles. The oxid of nitrogen is ab- 

 sorbed, furnishing a dilute nitric acid. This is then pumped to large 



