146 SPECTRA OF THE HALOGENS. PARTI. 



has found that a similar difference prevails in the 

 spectra of carbon compounds when in a state of incan- 

 descent gas, which have hitherto been supposed to yield 

 the same spectrum. ' The spectrum obtained from the 

 flame of olefiant gas is different from that obtained by 

 the electric discharge through a vacuum of the same 

 gas; while the spark passing through a cyanogen 

 vacuum produces a spectrum identical with that of the 

 olefiant gas flame, and through the carbonic oxide 

 vacuum a spectrum coincident with that of the spark 

 through olefiant gas vacuum. 5 



The chlorides, bromides, and iodides are the most 

 easily vaporized of all the metallic salts, and give the 

 most brilliant flames and the most intense spectra, 

 especially the chlorides. A small piece of the chloride 

 of barium volatilized by a colourless gas flame tinges the 

 flame green, and the red and green lines on the spec- 

 trum stand out with extreme brilliancy. The scattered 

 yellow light on the spectrum of the chloride of sodium 

 is comparatively dark by contrast with the bright 

 lines, and upon shading off the more luminous part 

 of it, traces of lines are visible in the more refrangible 

 portion. 



Chloride of lithium gives the red and orange lines on 

 its spectrum ; the brilliant blue band discovered by Mr. 

 Tyndall, and another more refrangible blue line is seen 

 when the ignition is at its greatest intensity. Chloride 

 of calcium gives a blue band very brightly, and several 

 other lines. The light of the chloride of copper is very 

 vivid, and its spectrum is remarkable for changing its 

 appearance with the decomposition of the chloride. 

 The chlorides of lead and cadmium, also, give very 

 bright and definite spectra, and chloride of bismuth 

 shows numerous brilliant red and blue rays which 

 quickly disappear. Thus the chlorides give spectra 

 with lines, such as the blue lithium and strontium 



