Flame Reactions of Thallium. 167 
carbon is found in the ordinary luminous flames’ and that the lumi- 
nescence is due to this carbon. Heumann’ pointed out that when a feebly 
luminous hydrocarbon flame be charged with chlorine or with bromine, 
the luminosity of the flame is greatly increased. The chemical activity 
of chlorine and of bromine brings about the separation of carbon, which, 
on incandescence, increases the luminosity of the flame. 
While investigating the structure of luminous flames, Smithells’ 
proved that free carbon is found in the luminous portion of a hydro- 
carbon flame. His conclusion, which is in agreement with the view of 
Kersten,' is that the separation of carbon in a flame is due simply to the 
decomposition of the hydrocarbon by heat. He also asserts that the 
glow of carbon in the luminous region is due to the heat of its own 
combustion, and is increased probably by the concomitant combustion of 
hydrogen. Smithells’ also succeeded in precipitating copper from a 
flame charged with cupric chloride. 
Hodgkinson® obtained a deposit of sulphur from a moderate-sized 
sulphur flame. 
Bancroft and Weiser,’ who experimented with a number of metallic 
salts, proved that these salts dissociate at the temperature of the Bunsen 
flame, of the hydrogen-air flame and of the oxyhydrogen flame, the 
metals being set free. 
Papish* investigated the behavior of compounds of selenium and of 
tellurium in the Bunsen flame and in the hydrogen-air flame. Elemen- 
tary selenium and tellurium can be easily obtained by depressing the 
flames with a cold object. 
In all cases mentioned above the luminescense can be traced back to 
the existence of an elementary substance in the flame. In some cases 
a particular luminescence is due to the existence or formation of a 
certain compound in a given zone of the flame. The work described in 
this paper was undertaken with the purpose of throwing more light on 
the nature of flame reactions in general and of the reactions of thallium 
in particular. 
Thallous Chloride in the Bunsen Flame.—“Chemically pure” thallous 
chloride was distilled and redistilled in a hard glass tube. The final 
1Hilgard: Liebig’s Ann. 92, 129 (1854); Liebig’s Jahresb. 1854, 287; Landlot : 
Poge. Ann. 99, 389 (1856). 
2 Chem. Centrb. 1. 1876, 801. 
3 Jour. Chem. Soe. 51, 223 (1892). 
4J. prak. Chem. 84, 290 (1861). 
5 Phil. Mag. (5) 39, 127 (1895). 
6 Chem. News 61, 96 (1890). 
7 Jour. Phys. Chem. 18, 259 (1914). 
8Tbid. 22, 430 (1918); Ibid. p. 640. 
