1882.] on Spectrum Analysis in the infra red of the Spectrum. 



63 



that if we could diminisli the hydrogen we might have something 



again different. 



Methyl iodide. 

 H 



I 

 H— C— H 



CI 



CI 



We therefore tried chloroform, and much to our surprise all the 

 broad bands had vanished, and we had a linear spectrum. "What 

 would happen if we removed the last hydrogen? In carbon tetra- 

 chloride the last hydrogen is removed, and we got no absorption 

 spectrum at all ; indicating that hydrogen had a most important 

 bearing on the absorptions. Carbon disulphide and cyanogen gave 

 us the same results. On the other hand, when we spectroscoped hydro- 

 chloric acid we had a linear spectrum, as we had with ammonia, 

 sulphuric acid, and nitric acid. Even water was found not to be free 

 from lines, as the boundary of each band was a line. I think, then, 

 that this satisfactorily settles the point that hydrogen gives the 

 initiative to all the special absorptions we noticed. The introduction 

 of oxvc^en skives shaded bands : but on measurement it was found that 

 shades were made up of step by step absorptions between two or more 

 positions of hydrogen lines. Again, what is called the radical of each 

 group of compounds was found to have a definite absorption in a 

 definite locality ; hence this spectroscopic method became a means of 

 qualitatively detennining the composition of an unknown compound 

 and its molecular structure. I would point out also how the absorp- 

 tions found by the photographic method go hand in hand with those 

 found by Professor Tyndall. In the annexed table we have the value 

 of the absorptions found by him, and following the absorption spectra 

 of the same bodies through six inches of liquid. The coincidence is 

 remarkable and worthy of attention. 



Absgeption of Heat by Liquids. 

 (^Source of Heat a Platinian Spit-y.^ ra's.d to Bright Ecdness by a Voltaic Current.) 



Carbon disulphide 

 Chloroform .. 

 Methyl iodide . . 

 Ethyl iodide 

 Benzine ., ' .. 

 Amylene 



Ether 



Alcohol 



Water 



