270 NITROGEN. 



support respiration. It was afterwards named nitrogen by 

 Chaptal, because it is an element of nitric acid. Besides 

 existing in air, nitrogen forms a constituent of most animal and 

 of several vegetable substances. In a natural arrangement of 

 the elements,, nitrogen is placed next phosphorus, and in close 

 relation with antimony and arsenic. 



Preparation. Nitrogen is generally procured by allowing 

 a combustible body to combine with the oxygen of a 

 certain quantity of air confined in a vessel. For that pur- 

 pose a glass flask may be inverted over a small jet of hy- 

 drogen, burning as it issues from the upright exit tube of a 

 gas bottle, till the flame goes out, which it does after exhausting 

 the oxygen in the flask. The flask is then removed from the 

 hydrogen bottle^ its mouth being closed with the thumb, and 

 conveyed to a pneumatic trough, where the residuary gas con- 

 tained in the flask may be transferred into a jar. Or a little 

 metallic or porcelain cup may be floated, by means of a cork, 

 on the surface of the water-trough. A few drops of alcohol are 

 then introduced into the cup, or a small piece of phosphorus 

 is placed in it, and being kindled, a tall bell jar is held over the 

 cup, with its lip in the water. The combustion soon termi- 

 nates, and the water of the trough rises in the jar. Alcohol 

 does not consume the oxygen entirely, a small portion of it still 

 remains mingled with the nitrogen ; a certain quantity of car- 

 bonic acid gas is also produced by its combustion. But the 

 combustion of phosphorus exhausts the oxygen completely, and 

 leaves nitrogen unmixed with any other gas. Nitrogen may 

 likewise be obtained by several chemical decompositions, which, 

 however, are more curious than important as sources of this 

 gas. Chlorine gas, for instance, conducted into diluted am- 

 monia, is absorbed and evolves nitrogen ; so do fragments of 

 sal ammoniac thrown into a solution of chloride of lime ; fresh 

 muscular flesh is also dissolved by nitric acid when heated, with 

 the evolution of nitrogen. 



Properties. Nitrogen gas is tasteless and inodorous; has 

 never been liquefied, and is less soluble in water than oxygen. 

 It is a little lighter than air, which possesses the mean density 

 of 79 volumes of nitrogen and 21 volumes of oxygen. Nitrogen 

 is a singularly inert substance and does not unite directly with 

 any other single element^ so far as I am aware, under the in- 

 fluence of light or of a high temperature. A burning taper is 



