62 SPECIFIC GRAVITY OF GASES. 



By comparing the numbers in the 3rd column 

 of the Table, down to nitrogen, with the atomic 

 weights in the preceding table, page 50, it will be 

 found that they are identical or, that the specific 

 gravity of the gases and vapours in the upper 

 department of the Table, corresponds with their 

 atomic weights, as deduced from the analysis of 

 compound bodies. From which it follows, that 

 equal volumes contain equal numbers of atoms. 



This however is not the case with the next 

 class of gaseous bodies ; for it will be observed, 

 that from ammonia down to bromide of mercury, 

 the atomic weights in the 3rd column are just 

 half of what they ought to be, were the atom 

 and the volume the same that is, allowing the 

 atomic weights in the first Table to be the true 

 ones. 



It will also be observed, that the specific 

 gravity of oxygen is 16 times that of hydrogen, 

 while its atomic weight is only 8 showing that 

 its specific gravity is double its atomic weight as 

 exhibited in the first Table. The difference is 

 still greater between the specific gravity of phos- 

 phorous vapour and its atomic weight, in the 

 ratio of 4 to Ior of 64 to 16. The same is true 

 of arsenic vapour, its specific gravity being 152 

 times that of hydrogen, and its atomic weight 

 only 38 while the specific gravity of sulphur 

 vapour is 6 times its atomic weight, the former 

 being 96, and the latter 16. 



