THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



♦ 



[FOURTH SERIES.] 

 AUGUST 1860. 



IX. Chemical Analysis by Spectrum-observations. 

 By Professors Kirchhoff and Bunsen*. 



[With a Plate.] 



IT is well known that certain substances possess the property of 

 imparting definite colours to flames in which they are heated. 

 When the coloured light thus produced is analysed by a prism, 

 spectra exhibiting differently coloured bands or lines of light 

 are seen. Upon the occurrence of these lines of light an en- 

 tirely new method of qualitative chemical analysis can be based — 

 a method which greatly enlarges the scope of chemical reactions, 

 and points to the solution of problems hitherto unapproachable. 

 In the present paper we shall confine ourselves to the application 

 of this method to the detection of the metals of the alkalies and 

 alkaline earths, and to the illustration of the value of the 

 method in a series of examples. 



The bright lines in the flame-spectrum are seen most plainly 

 when the temperature of the flame is highest, and its illu- 

 minating power least. The laboratory-lamp described by one 

 of usf, in which a mixture of air and gas burns, gives a flame 

 of extremely high temperature and very slight luminosity, and 

 is therefore especially well adapted for experiments upon the 

 bright lines produced in the way described. 



Plate II. represents the spectra given by a colourless flame in 

 which chemically pure salts of potassium, sodium, lithium, 

 strontium, calcium, barium are allowed to volatilize. The solar 

 spectrum is added for the sake of comparison. 



The potassium compound employed was obtained by igniting 



* Communicated by Professor H. E. Roscoe. 

 t Poggendorff's Annalen, vol. c. p. 85 ; Phil. Trans. 1857, p. 377- 

 Phil Mag. S. 4. Vol. 20. No. 131. Aug. 1860. H 



