420 NITROGEN 



point of water is converted into a crystalline solid. It is nearly insoluble in wate? ; 

 but alcohol and ether dissolve it in all proportions. Its conversion into aniline under 

 the influence of reducing-agents has been before mentioned. See ANILINE. 



Nitrobenzol may be viewed as having been derived from benzol, C 12 H 6 (C 6 H 6 ), 

 by the substitution of one equivalent of hydrogen by the tetroxide of nitrogen. 



NITROGEN. Symbol, N; equivalent, 14; combining -measure, two volumes; spe- 

 cific gravity, 0-97 13; Syn. Azote. ( Nitrogene, Azote, Fr. ; Stiokstoff, Salpeterstoff, Ger.) 

 This gas, which serves so important a purpose in diluting the atmospheric oxygen to 

 the point necessary for healthy respiration, has been known, in a more or less im- 

 pure state, since 1772, when Dr. Kutherford showed that the vitiated air from the 

 lungs contained a principle incapable of supporting life, but differing from carbonic 

 acid. 



Preparation. Nitrogen is usually prepared from atmospheric air by removing its 

 oxygen. This may be done in a variety of ways : 1. By burning some substance in 

 a confined portion of air, and removing the oxide by a solvent. Thus, alcohol burnt 

 in air yields nitrogen, water, and carbonic acid, The water condenses, and the car- 

 bonic acid may be absorbed by agitation with lime-water. The oxygen may also be 

 taken away by the combustion of phosphorus. The phosphoric acid produced, being 

 soluble in water, is easily removed. 2. The most elegant mode of obtaining the 

 nitrogen, and one which, properly performed, is susceptible of the highest quantitative 

 accuracy, is to pass air over red-hot copper, which absorbs the oxygen, forming oxide 

 of copper, pure nitrogen remaining. 3. The oxygen of atmospheric air may also 

 be removed by certain solvents. A solution of pyrogallate of potash, or, rather a 

 solution of pyrogallic acid in an excess of potash, takes the oxygen from air with 

 great rapidity and great precision. Upon this fact Liebig founded his process for 

 estimating the percentage of oxygen in certain gaseous mixtures. A very pure 

 nitrogen may be obtained, according to Corenwinder, by heating a solution of nitrate 

 of potash with chloride of ammonium. Nitrogen may be obtained from ammonia by 

 the action of chlorine, which combines with the hydrogen. Flesh gently heated with 

 diluted nitric acid yields the gas, contaminated with its binoxide. The latter may 

 conveniently be got rid of by passing the gases liberated through two Liebig's potash- 

 bulbs filled with a moderately-concentrated solution of protosulpbate of iron. 



Properties. Nitrogen has, especially until lately, been regarded as one of the most 

 inert of the elements, as a body with but slight tendency to enter into combination, and, 

 when combined, being easily removed by even the least energetic reaction. This opinion 

 has been founded on too limited a study of its properties. It is true that with some 

 elements it unites but feebly, and such combinations are, in a few cases, decomposed by 

 the slightest causes ; and, in the case of the so-called iodide and chloride, by mere friction 

 or percussion. But the energies of nitrogen are not to be estimated from these com- 

 pounds alone. There are bodies with which it exhibits an intense desire for union ; 

 among these may be mentioned carbon, titanium, and boron. Hydrogen and certain 

 organic groups also unite readily with nitrogen, forming stable and highly character- 

 istic classes of compounds. 



Determination of the Purity of Nitrogen Gas. The simplest and most accurate process 

 is that of M. Bunsen. The first thing is to determine whether a combustible gas 

 containing oxygen be present. For this purpose it is merely necessary to pass an 

 electric spark through the gas contained in a eudiometer. If the bulk remains un- 

 altered the absence of any considerable amount of combustible gas mixing with oxygen 

 is proved. But they may be present in such small quantity, as compared with the 

 noncombustible gas, that no explosion can ensue on passing the spark. It is then 

 necessary to add some battery-gas in order to render the mixture inflammable. [By 

 ' battery-gas ' is understood the gas obtained by the electrolysis of water.] For the 

 purpose of the experiment, we may add to every 100 volumes of the gas under exa- 

 mination 40 volumes of battery-gas. If the volume after explosion bo unaltered, the 

 total absence of oxygen and combustible gases is demonstrated. It is still possible 

 that the nitrogen may be contaminated with oxygen, although inflammable g;iscs are 

 absent. To determine this fact we must add both hydrogen and battery-gas in such 

 proportions that the volume of the original gas plus hydrogen is to that of the 

 battery gas as 100 : 40. If no oxygen be present the volume after explosion will be 

 that of the original gas and the hydrogen ; the reason being that if oxygen had been 

 present some of the hydrogen would have disappeared in order to form water. The 

 nitrogen gas may still be contaminated by a trace of a combustible gas. To deter- 

 mine this point as much common air is to be added to the last mixture containing 

 hydrogen as will form a detonating mixture with that hydrogen. This detonating 

 mixture so produced should form from 26 to 64 per cent, of the incombustible gases. 

 If, on making the explosion, it is found that two-thirds of the condensation is equal to 



