Minor Constituents of Air 231 



white pentoxide of phosphorus, has been produced, 

 there has been no complete destruction nor any creation 

 of matter. The phosphorus still exists, no longer in 

 the free state, but combined with oxygen ; some of 

 the latter has also changed from the free to the combined 

 state. To show that the oxygen, or some part of it, 

 has been removed from the air, remove the wire from 

 the cork, and open the mouth of the flask under water. 

 A certain amount of the latter will pass into the flask. 

 (Compare Experiments 79 and 80.) Recork the flask 

 under water, remove it from the water and shake it 

 well. When the oxide of phosphorus has dissolved, 

 remove the cork, and insert a lighted taper. The gas 

 left in the flask will not support combustion, if sufficient 

 phosphorus has been used to combine with all (or most 

 of) the oxygen originally present in the flask. 



If, in any other experiment, the total quantity of 

 stuff, whether gaseous, liquid, or solid, taking part in 

 the experiment, together with all the apparatus used, 

 be weighed under similar conditions before and after 

 the performance of the experiment, it will be found 

 that the original weight is unaltered. 



Hence, although we may readily bring about the 

 transformation of one kind of matter into another, we 

 can neither destroy nor create matter. This last 

 statement is known as " the Principle of the Inde- 

 structibility of Matter ", and is one of the most 

 important principles of science. 



158. Since the processes of combustion and animal 

 respiration both produce carbon dioxide and water- 

 vapour, and are both continually going on in the world 

 around us, it seems likely that the atmosphere will 

 contain some carbon dioxide and some water-vapour. 



