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XXV. 



THE QUANTITATIVE SPECTEA OF LITHIUM, RUBIDIUM, 

 CAESIUM, AND GOLD. 



By A. G. G. LEONARD, A.R.C.Sc.T., B.Sc, Ph.D., 



AND 



P. WHELAN, A.R.C.Sc.1. 



(Plate XVI.) 



[Read January 22 ; published February 15, 1918.] 



This work is a continuation of that begun in 1907 by Pollok and Leonard 1 

 with a view to facilitating the use of the spectrograph in detecting the 

 metallic elements when present in solution in small quantities. 



It was then pointed out that a knowledge of the metallic lines, which 

 appear in the spark spectra of dilute solutions, is of great importance from 

 the analytical standpoint. The strongest lines of the metallic spectra are not 

 necessarily those which have the greatest persistency as solution lines, and, 

 consequently, the identification of the metals in a dilute solution by com- 

 parison of the few lines observed with a complete list of all the lines in the 

 spectrum becomes laborious and, in many cases, uncertain. 



Knowledge of the dilution spectra, on the other hand, renders identifi- 

 cation rapid and certain. 



The work was carried out with a one-prism quartz spectrograph recently 

 purchased from Messrs. Hilger of London. The dark slide is so made as to 

 take specially thin glass photographic plates in slightly curved form, by which 

 means the whole spectrum from A 7000 to A 2000 is received on the plate in 

 very good focus. This effects a considerable saving in time, as it obviates the 



1 Proo. R. D. S., vol. xi, 1907, pp. 184, 217, 229. 



