GASEOUS BODIES. 



Hydrogen, Chlorine, and Azote. There are 

 seven simple bodies which are capable of com- 

 bining with hydrogen, and forming with it a 

 gaseous compound : these are iodine, carbon, 

 phosphorus, sulphur, selenium, arsenic, and tel- 

 lurium. The two remaining bodies, boron and 

 silicon, enter into gaseous combinations with fluo- 

 ric acid,- a substance, the consideration of which 

 is deferred till a future chapter ; though the 

 specific gravity and atomic weights of the gases 

 will be inserted in the following tables, for the 

 sake of completing the series of gaseous bodies. 

 Gases 2. We have seen that water is a compound of 



dfic gravity one volume of oxygen gas, and two volumes of 

 hydrogen gas ; while, from the proportion in 

 which hydrogen combines with all known bodies, 

 there is every reason to consider two volumes of 

 it as equivalent to an atom ; or if we choose, for 

 the sake of simplicity, to represent an atom of 

 hydrogen by a volume of the gas, then we must 

 represent an atom of oxygen by half a volume of 

 the gas. We have seen that chlorine and azote 

 have the same relation between their atomic 

 weights and their volumes that hydrogen has; 

 this is the case also with iodine, carbon, phos- 

 phorus, and sulphur, when in the state of va- 

 pour. The relation between the atomic weight 

 and the volume of the vapours of selenium, ar- 

 senic, and tellurium, has not yet been determin- 

 ed by experiment ; but there seems no reason 



= atom X 

 555. 



