Properties of Pure Substances : Nitrogen. 19 



yielded a fine band-spectrum which has been described often 

 enough, showing well both in the more and less refrangible 

 ends. I took as my authority on the typical hydrocarbon 

 bands those mentioned in the B.A. Report for 1880, p. 226. 



Observer. Wave-length. 



C Angstrom and Thalen . . 5633 at least refran- 

 1 gible end. 



(Watts 5634-7 



f Angstrom and Thalen . . 5164 

 \ Watts 5165 



f Angstrom and Thalen . . 4736 

 1 Watts ..."..... 4739 



Professors Liveing and Dewar (Proc. Roy. Soc. vol. xxx.) 

 say that the characteristic spectrum of hydrocarbons is com- 

 posed (among others) of four bands in the orange, yellow, 

 green, and olive. These were well seen by me in an olefiant- 

 gas tube prepared for the purpose without any pretensions to 

 purity. The cone of a Bunsen flame was also examined, and 

 I saw the lines (according to my map) 



a at 5637 instead of 5634 



j3 „ 5164 „ 5165 (strongest) 



7 „ 4736 „ 4738 



1 had a number of commercial tubes and examined these as 

 a check ; the following is the result : — 



/3 turned up in petroleum and alcohol but not in olefiant gas, 

 where there was a band at 5197 to 5198. This last band was 

 strong and was seen in C0 2 , H, 0, turpentine, petroleum, and 

 coal-gas, as well as in the defiant gas. I do not know what 

 this band is due to, but it did not appear in the nitrogen. 

 The nitrogen Avas examined side by side with an alcohol tube 

 showing a and ft well ; but the former did not show these 

 bands or any trace of them. The nearest band was at 5240, 

 and quite too far away for there to be any mistake. The 

 experiment was also tried with a similar tube and nitrogen at 

 10 millim. pressure, with a like result. Finally the examina- 

 tion was repeated at the lowest pressure at which I could get 

 a brilliant discharge, which was of course far beyond the 

 limit of discrimination of my pressure-gauge. The result 

 was the same as before. The red and blue hydrogen lines 

 were never seen in any of my tubes showing banded spectra. 

 This analysis is of course dependent partly on the accuracy of 

 our map, though when once the typical lines were picked up, 

 their coincidence or not could be determined bv direct expe- 



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