ABSORPTION TOWERS 315, 



ted and recombined incessantly in such a way that the total 

 percentage of the oxid of nitrogen remains constant in the mix- 

 ture. 



274. Oxidation Towers. These large reservoirs communicate 

 with the electric furnaces by large tubes and are two in number. 

 They are cylindrical in shape and in the interior are covered by 

 a material which is not attacked by acids. In these towers the 

 further oxidation of the oxid of nitrogen produced in the furnace 

 takes place. In a short time in these towers the oxid of nitrogen 

 (NO) is converted into NO 2 . Leaving the reservoirs, the nitrous 

 gas produced is forced through a ventilator into the absorption 

 lowers where it is transformed into nitric acid. The transforma- 

 tion which takes place in these last towers, converts the nitrous 

 oxid into nitric acid by means of water according to the formula, 

 2NO 2 +H 2 O=HNO 3 -f HNO 2 . At the same time that the nitric 

 and nitrous acids are formed there are produced lower oxids of 

 nitrogen by the decomposition of nitrous acid according to the 

 following equation: 2HNO 2 =NO 2 -f NO+H 2 O. These are re- 

 oxidized by the continuous fundamental reaction. 



275. Absorption Towers. These are prismatic in shape, having 

 a section four meters square and 10 meters high. They con- 

 tain, therefore, 40 cubic meters. They are placed along the sides 

 of a hall in two parallel rows, each row embraces two towers in 

 granite and two towers in sandstone, filled with pieces of quartz 

 of the size of the thumb, two-thirds of their height. In the in- 

 terior of these towers there are circulated in an inverse direc- 

 tion and in a continuous manner the gases and the water. This 

 water, which constantly moistens the quartz, is charged pro- 

 gressively with the nitric acid which is formed. The other nitrous 

 products, with the exception of the lower oxids, which accompany 

 the formation of nitrous acid, are reoxidized in these towers in 

 contact with the oxygen of the air, and give new quantities of 

 nitrous acid, as has just been described. Finally, when the solu- 

 tion of nitric acid produced in the towers has attained by re- 

 peated contact with the gases and water a concentration of 50 

 per cent., that is, 50 kilograms of monohydrated nitric acid in 

 100 liters of liquid, it is received into ordinary vessels made of 



