. Elementary physics and chemistry: second stage . Another way is to burn a little phosphorus in a sealed tube having a pointed end, and then by breaking off the end of the tube under water, the volume of water which takes the place of the air used can be found, and its proportion to the whole volume of the tube can be determined. That the gas left be- hind is really the inactive part, which is called nitrogen, can be proved by quickly pulling out the stopper of a jar in Fig. 58.—Phosphorus uses up one-fifth of the air 1 • 1 1 , v in the bottle when it burns, and water rises to take which phos
. Elementary physics and chemistry: second stage . Another way is to burn a little phosphorus in a sealed tube having a pointed end, and then by breaking off the end of the tube under water, the volume of water which takes the place of the air used can be found, and its proportion to the whole volume of the tube can be determined. That the gas left be- hind is really the inactive part, which is called nitrogen, can be proved by quickly pulling out the stopper of a jar in Fig. 58.—Phosphorus uses up one-fifth of the air 1 • 1 1 , v in the bottle when it burns, and water rises to take which phosphorus has the place of the air used. been burnt, and intro- ducing a lighted taper. The flame is at once extinguished. Phosphorus slowly takes out the active part of the air without being lighted.—We have seen that iron slowly takes the active part of the air and combines with it to form rust. And this happens without heating the iron. Will ordinary phosphorus do the same when it is not ahght ? This question, too, is easily answered by a simple experiment. When a piece of clean phosphorus is exposed to an enclosed quantity of air over water, the rapid changes described in the last paragraph take place slowly. The only difference in the two cases is the rate at which the active part of the air is taken out. Burning phos- phorus combines with the active part very quickly ; ordinary phosphorus but slowly. Still, given time enough, ordinary phosphorus will remove all the active part of air, and at the end of the experiment it will be found that again one-fifth of the air has disappeared. To BE Remembered. Phosphorus readily burns in the air ; in doing so it takes out the active part and combines with it to form a white snow-like powder. Phosphorus can also, like iron, slowly take out the active part of the air without being lighted. When phosphorus is burnt in an enclosed volume of air, one- fifth of the volvnne is used up, and four-fifths remnin.
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