346 Hartley and Ramaor — Banded Flame- Spech-a of Metals. 



As in the zinc-spectrum, the bands can be distinguislied as far as the edge of 

 the plate (X 3530), but the component lines of the bands are too nebulous and 

 feeble to admit of accurate measurements. The lines are much more widely 

 separated towards wave-length 3530. The lines in the spark-spectra are not 

 identical with those in the flame-spectrum, though several of them have nearly 

 the same wave-leng^th. 



Flame-Spectra of Aluminium, Gallium, Indium, and Thallium. 



The oxyhydrogen flame-specti'um of aluminium, really of the metal burning 

 in the flame, is a channelled spectrum of fine flutings degraded towards the red* 

 It contains the bands which occur in the " arc-spectrum of aluminium oxide, "f 

 and in the spark-spectrum under certain conditions. J 



When aluminium burns in the oxyhydrogen flame, the energy of the 

 combustion is sufficient to volatilise some of the metal, and the flame is coloured 

 blue. This colour is also seen in the flame when oxide of aluminium, in the form 

 of thin rods, is heated in the hottest part of the flame. A stronger spectrum 

 was obtained when a mixture of aluminium oxide, with a dense form of carbon, 

 such as gas carbon or graphite, was heated. The doublet of aluminium, wave- 

 lengths 3967 and 3946, was photographed by this method, but the bands have not 

 been obtained in the same way. 



Hemsalech confirms Aron's view, that the bands are really due to the metal, 

 and not the oxide of aluminium. § 



No bands have been observed by us in the spectrum of gallium, || but the metal 

 is so scarce, that no opportunity has occurred in which to examine the spectrum 

 thoroughly. 



Flutings not previously observed have been photographed in the flame- 

 spectrum of indium, and in that of thallium ; they are very much weaker than 

 the lines of the strong doublets of indium with wave-lengths 4511 and 4102, 

 and of thallium 5314 and 3775. 



* Hartley, Phil. Trans., vol. 185 (A.), 1894, p. 211. 

 fHasselberg, " Kongl. Svenska Vet.-Akad. Hand.," B. 24, 1892. 



I Hemsalech, Ann.der Physik, 2, June, 1900, pp. 331-4. 

 § Loc. cit, 



II The authors have discovered and directed attention to a convenient source of this metal. The cost 

 of extraction will he very much less than by the process employed for extracting gallium from blende. 



