NITRO-BENZENE 470 NITROGEN temperature there is a proportionate in- crease of work — commencing at about 12° C. — till 37° is reached, which is the "optimum" temperature, and from this onward there is a diminution of action until the "maximum" temperature of 55° C. is reached, when nitrification ceases. These bacteroids are annihilated at a temperature of 90° C, although the same result will follow drying even at a much lower temperature. The second condition is the presence of oxygen; and the third is the presence of a salifiable base, such as lime, potash, soda, etc., without which nitrification cannot pro- ceed. Under these conditions nitrifica- tion goes on in every fertile soil, the at- mospheric nitrogen, nitrogenous organic matter, or ammonia compounds being converted, in the presence of lime or pot- ash, into the corresponding nitrates of lime or potash; and from these nitric compounds plants derive the most or all of their nitrogen. NITRO-BENZENE, an oily body pre- pared by gradually adding benzene to cold fuming nitric acid. It is a yellowish liquid with a sweet taste, and an odor of oil of bitter almonds. Much used by perfumers under the name of oil of mirbane, and manufactured in large quantities for the preparation of aniline and its derivatives. NITROCELLULOSE, the product of the reaction between cellulose and nitric acid. The name is generally restricted to the product formed by the nitration of cotton, which consists of a mixture of nitrocelluloses and is known as gun- cotton. When strong acids are used and the process of manufacture properly conducted, guncotton consists chiefly of tri-nitrocellulose, CbHtOj (N03)s, but di- tetra and penta-nitrocellulose are usually present. Nitrocellulose was first made in 1832 by Braconnot, by treating starch with nitric acid. Its explosive proper- ties were discovered by Schonbein in 1845. It is insoluble in water, soluble in a mixture of alcohol and ether, and in ethyl acetate, nitrobenzene, benzol, acetone, amyl acetate and ketone oils. When cotton is treated with nitric and sulphuric acid in the presence of water, collodion cotton, CsHaiOoCOH) (N03)8 is produced. This material is used in the manufacture of collodion varnish, pyrox- ylin, artificial leather, celluloid, and many other products. The cotton used in making nitrocellulose must be free from oil and rosin, and after the acid treatment it must be washed until all traces of acid are removed. NITRO COMPOUNDS, compounds in which one or more atoms of hydrogen are replaced by an equivalent quantity of nitryl (NOa) ; thus, lactic acid CsHeOs, becomes nitro-lactic acid CaHs (N03)0». The nitro compounds are nitro-marin, nitro-tartaric acid, nitro- saccharose, benzoic acid, nitro-carbolic acid, nitro-coumarin, etc. NITROGEN, N., at. wt. 14.01, color- less, odorless, tasteless gas, forming, ap- proximately, four-fifths of the atmos- phere. Slightly lighter than the air. Discovered in 1772 by Rutherford, in the University of Edinburgh. It can be pre- pared by passing air over some reagent which will readily react with and ab- sorb oxygen, such as reduced iron, alka- line, pyrogallol, or phosphorus; or by liquefying air and distilling, when the more volatile nitrogen is vaporized. Ni- trogen is found in all vegetable and ani- mal life, usually in organic combination, and in varying quantities in the earth's crust in both organic and inorganic com- bination. It is a necessary constituent of plant and animal food. Certain leg- umes have the power of fixing the nitro- gen of the air by means of root nodules, and obtain their supply in this way, while electric discharges in the atmos- phere cause the union of nitrogen and oxygen, the resulting oxides of nitrogen being washed into the soil by rain. These sources are not sufiicient, how- ever, to enrich the soil to the extent needed for intensive cultivation, and by far the greater part of nitrogen is added, either in the form of decompos- ing organic matter (barnyard manure, guano, etc.) or inorganic salts (nitrates, ammonium sulphate, etc.). The most commonly used inorganic nitrogenous fertilizer is sodium nitrate or Chili salt- petre, NaNOs, but it is believed that the supply of this material will become ex- hausted in less than forty years. More- over, nitrogen in the form of nitric acid, nitrates, or ammonia is an important raw material in the manufacture of ex- plosives, dyes, sodium bicarbonate, and other products, while ammonia is widely used for refrigeration. The supply of nitrogen in the atmosphere is practically inexhaustible, the air over every acre of ground being estimated to contain 31,000 tons of nitrogen, and many attempts have been made to manufacture nitro- genous compounds from this source. Three methods have given successful re- sults on a manufacturing scale :^ (1) the formation of ammonia by combining the nitrogen with hydrogen; (2) the forma- tion of oxides of nitrogen by passing an electric arc through air, and (3) the for- mation of cyanamide by absorbing nitro- gen in calcium carbide, heated to white heat in an electric furnace.
