156 Intelligence and MisceUaaeous Articles, 



ox THE PRIMAHY SPECTRUM OF IODINE. NOTE BY M. G. SALET. 



The emission of a red light b}' the vapour of iodine strongly 

 heated appeared to me so interesting that I M^as induced to study 

 more closely the spectrum of that metalloid. 



MM. Pliicker and Hittorf did not succeed in producing with iodine, 

 by means of Geissler's tubes, a spectrum of the first order corre- 

 sponding to the absorption-spectrum ; I have been more fortunate 

 by employing a sheathed tube ; for I have been able at AviU, and in 

 the same apparatus, constructed entirely of glass, to obtain the line 

 spectrum described by Pliicker and also a new spectrum, of which 

 the less-refrangible part represents, so to say, the negative proof of 

 the fine absorption-spectrum so well studied by M. Thalen. It is 

 accompanied by excessively diffuse bands in the commencement 

 of the blue and the end of the indigo. These bands become more 

 luminous when the tension of the vapour is increased; but then 

 the lines of the secondary spectrum appear. The light of the tube 

 is of a bronzy yellow in the cold ; it becomes violet-blue with heating. 



To obtain the new spectrum, it is important to use an electric 

 source of feeble tension, such as the induction-coil accompanied by 

 a jar. It is not very bright, unless particular skill is employed for 

 its observation and the section of the narrow tube is presented to 

 the spectroscope. Each bright band, brought under the cros5-^^ire9 

 of the telescope, is replaced by a black band when the vapour is illu- 

 minated from behind. 



Here, then, is a fresh example of multiple spectra. It cannot be 

 supposed that the substance furnishing the new spectrum is a com- 

 pound of iodine ; for it would be the same compound that gives the 

 bands so well known of the absorption-spectrum; in other terms, 

 the characteristic coloration of iodine, that from which it derives its 

 name, would be due to an impurity. 



It therefore seems to me proved that one and the same elementary 

 substance may have two spectra, as it may have two allotropic states. 

 This was Pllicker's old opinion. 



It became interesting to know if the continuous spectrum of 

 iodine heated to redness would show indications of the primary 

 bands, as required by the theory of the proportionality of the emis- 

 sive and absorptive powers. By securing the most favourable con- 

 ditions and employing strong dispersion, I have in fact succeeded in 

 detecting the jjrincipal of them. — Comptes Rendus de V Acad, deb 

 Sciences, July 8, 1S72, pp. 76. 77. 



OX A SIMPLE APPARATUS FOR THE PRODUCTIOX OF OZOXE TTITH 

 ELECTRICITY OF HIGH TEXSIOX. BY PROF. ARTHUR W. 

 WRIGHT. 



Experiment has shown that in the production of ozone by elec- 

 tricity the maximum amount of oxygen is ozonized by the silent or 

 glow discharge : and most of the forms of apparatus by which this is 

 affected are contrivances by which oxvsren is made to flow slowly 



