166 Proceedings of Indiana Academy of Science. 
FLAME REACTIONS OF THALLIUM. 
JACOB PAPISH, Purdue University. 
The terms spectra of the first and of the second order were given by 
Pliiker and Hittorf* to what are known now as band and as line spectra. 
Mitscherlich* proved that the channeling of the band spectrum is due to 
‘the existence of a compound of a metal in the flame, while the line spec- 
trum is produced by the elementary metal. When halogen compounds 
of barium are introduced in the Bunsen flame they produce their own 
fugitive spectra, but on dissociation in the flame they all exhibit the 
band spectrum of barium oxide and also the }-line (—5535.69) of the 
metal. Mitscherlich’s work points to the fact that the final spectrum 
produced by a halogen salt of barium is the result of a chemical change 
that had been undergone by the salt in question. 
The well-known luminescence of a flame charged with compounds of 
sodium is undoubtedly due to the existence of metallic sodium in the 
flame. Mendeléeff’ arrived at this conclusion from the following experi- 
ments: If hydrochloric acid gas be introduced into a flame colored by 
sodium it is observed that the sodium spectrum disappears, owing to the 
fact that metallic sodium cannot remain in the flame in the presence of 
an excess of hydrochloric acid. The same thing takes place on the 
addition of ammonium chloride, which in the heat of the flame gives 
hydrochloric acid. If a porcelain tube containing sodium chloride (or 
sodium hydroxide or carbonate), and closed at both ends by glass plates, 
be so powerfully heated that the sodium compound volatilizes, then the 
sodium spectrum is not observable; but if the salt be replaced by sodium, 
then both the bright line and the absorption spectra are obtained, ac- 
cording to whether the light emitted by the incandescent vapor be 
observed, or that which passes through the tube. Thus the above spec- 
trum is not given by sodium chloride or other sodium compound, but is 
proper to the metal sodium itself. If every salt of sodium, lithium and 
potassium gives one and the same spectrum, this must be ascribed to 
the presence in the flame of the free metals liberated by the decom 
sition of their salts. 
Reference has been made from time to time to the fact that free 
1 Phil. Trans. 1885, 155. 
* Pog. Ann. 116, 419 (1862) ; 121, 459 (1863). 
°“Principles of Chemistry’, 1, 563 (1891). 
