OF BROMINE AND OE IODINE MONOCHLORIDE. 
209 
free from iodine. In order to remove any chlorine which might be present, it was 
digested with powdered potassium bromide for several weeks, again distilled, and treated 
with phosphorus pentoxide. The pure bromine boiled constantly between 59°-6 and 
59°-7 (corrected). Bar. (corrected and reduced) 765’2 millims. 
The spectrum was obtained by allowing the rays from a lime-light to pass, before 
falling on the slit of the spectroscope, through bromine vapour contained in a long and 
strong narrow glass tube heated by means of a flame. The spectrum thus obtained is a 
channelled one, and consists of a large number of bands, 66 of which have been 
measured. Each band, like those of iodine *, is made up of a close association of fine 
lines, the whole stretching from wave-length 6801-5 in the red to wave-length 5244-1 
in the green. Beyond these extremes the general absorption becomes too powerful to 
permit further bands to be seen. Each of these bands has a well-defined edge towards 
the blue end, and shades off gradually towards the less refrangible end of the spectrum, 
as shown in the drawing. The bands are by no means regularly dispersed throughout 
this length, but are more numerous, as well as more intense, in the yellow and green 
portions of the spectrum than in the red. The bands in the green form the best 
defined portion of the bromine spectrum, and the bands 5483-8 and 5460-1, although 
rather fainter than some others, are especially characteristic. The spectrum of the vapour 
of bromine at the ordinary temperature and that obtained when the vapour is heated 
differ from each other, inasmuch as the lines in the green beyond 5433-2 and in the red 
beyond 6101-4 are invisible in the cold, though visible in the heated vapour. A few 
lines, such as 5634*8 and 5580*6, in the green appear in the spectrum of the heated 
vapour, but not in that of the cold vapour ; but, as a whole, the bands seen in the cold 
vapour are also seen in the heated vapour, and no change whatever in position is noticed. 
The least refrangible bands beyond 6526‘9 are ill-defined ; they appear directly upon 
heating, but fade quickly away as the vapour cools. The letter f placed after the 
wave-length denotes that the line is faint ; v. f means very faint ; and s denotes that 
the line is dark and well-defined. 
TsALfjif, ‘ Le Spectre d’absorption de la vapeur d’lode,’ Upsal, 1869. 
