Absorption Spectrum of Iodine and Bromine. 423 



available. At a slight additional cost this slide-wire can be 



made an integral part of the apparatus, 

 sented a rather more elaborate design. 



Fig. 5. 



In fig. 5 is repre- 

 The slide-wire is 



^4 



x 



x±j 



T H *~7 



V7* 



B-~ 



easily recognized. The contact-piece of the slider S must be 

 made adjustable so as to be able to press on either part of 

 this wire. The circle K represents an ordinary Wheatstone- 

 bridge key. 



It will be seen that this design is very self-contained. All 

 the connexions to be made consist of : a battery, with its 

 supplementary resistance, to the binding-screws B, B', a 

 galvanometer to g and S, and two resistances between X, Y 



and Y, Z 



coils, and 

 sistance. 



The former, marked R 1? is an adjustable box of 

 the latter, R 2 , is a single coil of 1000 ohms re- 



XLIV. On the Absorption Spectrum of Solutions of Iodine 

 and Bromine above the Critical Temperature. By R. 

 W. Wood *. 



IN examining solutions of iodine above the critical tempera- 

 ture with a spectroscope, I have found that the fine lines 

 which characterize the absorption spectrum of gaseous iodine 

 may be either present or absent, depending on the amount 

 of the solvent present. 



These lines are not present in the spectrum of iodine 

 solutions, and their disappearance under the above-mentioned 

 conditions seemed to be due either to the pressure exerted by 

 the vapour, or to something akin to solution. 



The tube containing the liquid was heated in an iron tube 

 provided with two vertical slits, cut opposite each other, for 

 the passage of a light ray, which was subsequently analysed 

 with a large spectroscope of high dispersion. 



* From the Zeitschrift fur Phys. Chemie. Communicated by the 

 Author, 



