ToL. VIII. No. 195. 



THE AGRICULTURAL NEWS. 



325 



-espre.ssing rnom which is usually darkened, and kept as cool 

 as possible, to guard against any changes in the character of 

 the delicate and unstable oil. In the expressing room each 

 workman is seated on a low stool, and has before him 

 a glazed earthenware bowl, across whiqh, and resting in 

 depressions in the rim, is a wooden md run through a good- 

 sized sponge. In his left hand the workman holds another 

 sponge, often cup-shaped, against which he presses the 

 outside of the peel, giving this a circular twisting motion. 

 By this means the walls of the oil cells are broken, and the 

 oil is S(jueezed out into the sponge to drip into the bowl. 

 In this, the oil ri.ses to the top of the water, and can be 

 decanted otf. The oil is filtered into large copper containers, 

 in which it is stored to await sale. Various machines have 

 been tried for expressing the oil, bnt so far without success. 

 The amount of oil obtained will vary largely, according to the 

 district and the season, but will average from 0'7 D). per 

 1,000 lemon peels to 1 lb., and, in rare cases, to as much as 

 li lb. (Xafaf Aijrinilliiral Jumna/, .Iu!y 1909.) 



THE MANUFACTURE OP IflTRATE OF 

 LIME. 



The following is abstracted from a paper on this 

 subject by Herr Sam Eyde of Christiania, which 

 appeared in the Jan mat of the Royal Society of 

 Arts : — 



In order to explain the llirkeland-Eyde method, it is 

 necessary first to describe the flames, consisting of arcs of 

 light, which are used in the electric furnaces. The forma- 

 tion of the Hinie occurs through an arc of th? electric flame 

 being formed between the points of the electrodes, wdiich are 

 close to each other. By this, an easily movable and flexible 

 current is established which, with the arrangements made, 

 will be found in a highly magnetized field. The electric arc 

 that has been formed moves, on account of this magnetic field 

 with great velocity perpendicularly to the lines of force, and 

 the electric arc's foot draws back from the points of the 

 •electrodes. AVhen the length of the electric arc increases, 

 the electric resistance becomes greater and the ten.sion 

 increases, until it becomes so great that a new electric arc 

 starts from the points of the electrodes. 



To regulate the current, an inductive resistance is u.sed 

 in series with the flame. With an alternating current, all 

 these arcs are formed in ojiposite directions and appear to the 

 ■eye to be circular discs. It appears that we have discovered 

 in this flame a powerful technical means for the oxidation of 

 the nitrogen of air. The flame in our furnaces burns with 

 a steadiness that is really astoni.shing. 



On electrodes of 1"5 cm. thick cnp[)er tubing, through 

 which water passes for cooling them, one can take up over 

 1,-500 horse-power, with a flame of I'S m. in diameter. The 

 chamber in which the flame burns is circular, of only a few 

 -centimetres width, and about 2 m. ini diameter. After 

 the oxide of nitrogen is formed in the furnace, it is converted 

 in the oxidation tank into peroxide of nitrogen, and in the 

 absorption towers into nitric acid. 



The flame chamber of the furnace is formed of fire-clay 

 brick; through the walls of this the air is conveyed to the 

 flame. The nitrous gases formed in the flame escape 

 through a channel made along the casing of the furnace, 

 which, like the flame chamber, is furnished with fireproof 

 lining. 



With this furnace we have achieved such steady working 

 that it burns for weeks without any regulation worth 



mentioning. It may further be stated that the maintenance 

 of the furnace and its repairs are simple to a degree, as the 

 most exposed portion.s, the electrodes, only require to be 

 changed every third or fourth week, and the fireproof masonry 

 every fourth to sixth month. 



The temperature in our flames exceeds .3,000, or perhaps 

 3,.j00, degrees Centigrade. The temperature of the escaping 

 gasesinay vary between SOO' and 1,000" C, during ordinary 

 working. Tiie furnaces are made of cast steel and iron, the 

 middle of the furnace being built out to a circular flame- 

 chamber. r,y aid of centrifugal fans, the air is brought into 

 each furnace through tubes from the basement. 



When the air in the flame-chamber has been treated by 

 the electric flame.s, the nitrous gases formed pass out through 

 a channel built along the casing of the furnace, and thence 

 out through the lower part of the furnace to two fireproof- 

 lined gas-collecting pipes, about 2 m. in diameter, which 

 convey the gas through the basement out to the steam boiler 

 house. In the boiler house the gas passes through four steam 

 boilers, in which the temjierature, which was, as mentioned, 

 1,000 degrees Centigrade, is reduced. The heat given ott" by 

 the gas is used for concentrating the proilucts, and in the 

 winter time for warming the factory buildings. 



The steam produced in the, boilers is utilized in the 

 further treatment of the products. In the boiler house there 

 are also two large and two small air-compressors, which 

 supply compressed air for pumping acids and lye in the 

 factory '.s various chemical departments. 



The gases pass on from the steam boilers through an 

 iron pipe into the cooling house, with the object of completing 

 the cooling commenced in the steam boilers. This cooling is 

 necessary in order to obtain a suitable ab-sorption. Each 

 cooler consists of a great number of aluminium tubes, over 

 which cold water runs, while the hot gases pass through them. 

 The temperature of the gas is considerably reduced. From 

 the cooling chambers, the gases go on to the oxidation tanks. 

 These oxidation tanks are vertical iron cylinders, lined 

 with acid-proof stone. The object is to give the cooled gases 

 a sutticient period of repose, in which the oxidation of the 

 oxide of nitrogen may have time to take place The necessary 

 amount of oxygen is present in ample quantity in the air 

 which accompanies the gases from the furnaces. From 

 the oxidatiim tanks the gases are led into the absorption 

 towers. All the towers are filled with broken quartz, which 

 is neither attected by nitrous gases, nor by nitric acid. To 

 assist the passage of the gases on their way from the 

 furnace.s, there are centrifugal fans, constructed of aluminium, 

 on each row of tow'ers. 



The gases enter at the base of the first tower, go up 

 through the quartz packing and thence, by a large earthen- 

 ware pipe, enter the top of another tower, through which 

 they pass downwards through the quartz at the bottom of 

 the third tower, and so on, until the air, relieved of all 

 nitrous gases, leaves the last tower. Water trickles through 

 the granite tower, and this is gradually converted into weak 

 nitric acid, while the liquid used in the wooden towers is 

 a .solution of soda. The absorbing liquid enters the top of 

 the tower and is distributed in jets by a series of earthen- 

 ware pipes, so that the [lermeating gases come into 

 immediate contact with the absorbing liquid. In the granite 

 towers nitric acid is thus formed, i and in the wooden lowers 

 a .solution of nitrate of soda. 



The final stage of the process is the neutralization of 

 the nitric acid thus obtained, by means of limestone. 

 From the liquid formed, solid ' nitrate of lime ' 

 (calcium nitrate) is separated by heating it in vacuun* 

 evaporators. 



