THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



DECEMBER 1875. 



L. Spectral- Analytical Researches. 



By R. Bunsen*. 



[With a Plate.] 



THE low temperature of the non-luminous gas-flame suffices 

 for the production of but a few of the spectra of the simple 

 substances and of their compounds ; by far the greater number 

 of the elements are vaporized at temperatures which can only be 

 attained by means of the electric spark. The employment of 

 spark-spectra in analytical research cannot be dispensed with in 

 those cases where a new element is sought for, or where indubi- 

 table proof is required of the presence of substances possessed of 

 properties so similar as to render uncertain their detection and 

 separation by ordinary reagents. So many difficulties, however, 

 stand in the way of the employment of spark-spectra, that this 

 important method of analysis has not as yet obtained a practical 

 recognition in chemical laboratories. Means have been wanting 

 for the production at any time of spark-spectra with the same 

 ease as attends the formation of flame-spectra ; the first part of 

 this paper will therefore be occupied with the description of a 

 battery and spark-apparatus which supply this want. The non- 

 existence of Tables of spectra suited to all practical requirements 

 is another difficulty in the way of the employment of these 

 spectra. 



There are, it is true, a number of measurements, for the most 

 part excellent ; but the purity of the material employed in 



* From Poggendorff's Annalen der Physik vnd Chemie, vol. civ. 

 pp. 230-252, translated by M. M. Pattison Muir, The Owens College, Man- 

 chester. 



Phil. May. S. 4. Vol. 50. No. 333. Dec. 1875. 2 E 



