. Elements of modern chemistry . adding a salt, suchas potassium or ammonium sulphate, to the bath. NITEOG-EN. Density compared to air . .Density compared to hydrogenAtomic weight N Nitrogen is one of the elements of the air, and it was fromair that it was first obtained in a pure state by Lavoisier andScheele, in 1777. To obtain nitrogen from the atmosphere itis only necessary to remove the other element, oxygen. Preparation.—A flat piece of cork, B (Fig. 52), floating inthe pneumatic-trough, supports a small capsule containing a fragment of phos-phorus. The latteris inflamed, a
. Elements of modern chemistry . adding a salt, suchas potassium or ammonium sulphate, to the bath. NITEOG-EN. Density compared to air . .Density compared to hydrogenAtomic weight N Nitrogen is one of the elements of the air, and it was fromair that it was first obtained in a pure state by Lavoisier andScheele, in 1777. To obtain nitrogen from the atmosphere itis only necessary to remove the other element, oxygen. Preparation.—A flat piece of cork, B (Fig. 52), floating inthe pneumatic-trough, supports a small capsule containing a fragment of phos-phorus. The latteris inflamed, and thecapsule immediatelycovered with a bell-jar. The heat pro-duced by the com-bustion at first ex-pands the air anddrives out a portion,but in a few minutesthe water rises inthe jar, taking theplace of the oxygenwhich has been con-sumed. When thephosphorus is extinguished, the experiment has water gradually dissolves the white smoke of phosphoricoxide which fills the jar, and there remains a colorless, irre-. FiG. 52. AMMONIA. 139 spirable gas that will not support combustion. This gas isnitrogen, still mixed with traces of oxygen and carbonic acid gas. Pure nitrogen may be obtained by passing a current of air,previously freed from moisture and carbon dioxide, through aporcelain tube containing incandescent copper. The copperabsorbs the oxygen, and pure nitrogen passes out at the endof the tube and may be collected over the pneumatic trough. Pure nitrogen may also be obtained by heating ammoniumnitrite in a glass retort; nitrogen and water are found.(NH*)NO == 2ffO + N^ Ammonium nitrite. Properties.—Nitrogen is a colorless gas, somewhat lighterthan the air. A litre of this gas weighs grammes. Itextinguishes burning bodies, and is not combustible itself; itproduces no precipitate in lime-water. Water dissolves only•^ of its volume of nitrogen at 0°. Animals are quickly suffo-cated in an atmosphere of pure nitrogen, but the gas does notexert a poison
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