PHOSPHORUS. 207 



in it, no alteration takes place in its volume. For 

 complete combustion, 1 volume of this altered 

 gas requires 1*25 volume of oxygen gas. By 

 the combustion, it is converted into water and 

 phosphoric acid. Complete combustion cannot 

 be induced with any smaller volume of oxygen 

 gas. When we pass an electric spark through 

 a mixture of 1 volume of the gas, and O7<5 vo- 

 lume of oxygen gas, a detonation takes place ; 

 but the residual gas occupies very nearly 1 vo- 

 lume. On adding 0*5 volume of oxygen gas, a 

 new combustion takes place, and the whole gase- 

 ous matter disappears. It would seem that, by 

 the first combustion, the whole phosphorus is 

 consumed, leaving the hydrogen very nearly 

 pure. It is obvious, that half a volume of the 

 oxygen gas was employed in converting the hy- 

 drogen of the gas into water. The remaining 

 O75 volume of oxygen converted the phosphorus 

 vapour into phosphoric acid ; but phosphorus 

 requires its own volume of oxygen gas for this 

 purpose. From this it is evident that the altered 

 gas is a compound of 



1 volume hydrogen gas . . 0-0694 



0-75 volume phosphorus vapour . - 6250 



0(5914 



Hence it contains just nine times as much phos- 

 phorus as hydrogen, and its specific gravity is 



