﻿Spectrum of Monatomic Iodine Vapour. 653 



It is obvious that in the case considered there exists a circu- 

 lation of the vapour, but, for the diameter of the joining 

 quartz tubes, no serious pressure differences could exist ; 

 besides, it was shown by Nernst * and his collaborators that 

 the dissociation formulae can be applied to a gas flowing 

 through a pipe, if the flow is not too quick a one. 



Fig. 1. 





Two main iodine spectra are known — a band spectrum and 

 a line spectrum. The most complete study of these spectra 

 was made by H. Konen f. Condensed, strong discharges in 

 narrow parts of the Geissler tubes give generally the line 

 spectrum ; with wide tubes and feeble discharges we obtain 

 the band spectrum. The first experiments to show the in- 

 fluence of the dissociation on the emission spectrum were 

 made by the author, using Geissler tubes of ordinary shape 

 with vertical capillary tube. No interesting results were 

 obtained. A new spectrum was observed when using a tube 

 "end on" with large central part, as is seen in fig. 1; the 

 central part B had a length of about 12 cm. and a diameter 

 of 1 cm.; the parts A, covered with tinfoil, had a diameter 

 of about 3 cm. and a length of about 8 cm. This tube, not 



* W. Nernst, Theoretische Chemie, 7th ed. p. 709. W. Nernst and 

 H. v. Wartenberg, Zeitschriftf. physik. Chemie, vol. lvi. p. 535 (1906). 

 t Annalen der Physik, vol. lxv. p. 265 (1898). 



