xx.] SPECTROSCOPIC CONFUSION. 283 



confusion. If we can attach certain spectroscopic characteristics 

 to certain molecular finenesses (as many chemists were prepared 

 to do before they found out where it would lead them), then 

 when we find ourselves in presence of the true chemical 

 molecule in each case we should expect to find similar spectra. 

 Thus, to give an instance, it was at first suggested that, since 

 "atoms " were supposed to give line spectra and " molecules '' 

 fluted spectra, cadmium and mercury vapour, the vapour densities 

 of which lead chemists to believe that they are dealing with the 

 " atoms " of these substances, should give us line spectra. This, 

 however, they do not do. 



The spectroscopic confusion will be gathered from the follow- 

 ing table : 



Hydrogen . . .No absorption. 

 Nitrogen ... No absorption. 

 Oxygen .... Flutings. 



Chlorine . . . Absorption in the blue, and flutings. 

 Bromine . . . Flutings. 



Iodine .... Flutings, with or without continuous absorp- 

 tion in the violet according to temperature. 

 Cadmium . . . Absorption in the blue. 

 Mercury . . . No absorption. 

 Phosphorus . . Probable flutings. 

 Arsenic . . . Probable flutings. 



Evidently therefore, so far as spectroscopic evidence is con- 

 cerned, these vapours do not exist in comparable molecular 

 conditions, and this at once explains the " anomalies." 



We are now in a position to consider the case of sulphur. 

 This body, which is well within the range of experiment, gives 

 us two vapour densities, which we can tabulate as follows : 



Vapour density. Atomic weight. 



Sulphur 



Above 1000 32 ) q9 



Below 1000 96 I 



