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.MR. CHARLES DE WATTEVILLE ON FLAME SPECTRA. 



CHROMIUM. 



The spectrum of this metal, obtained by using a concentrated solution of chromic 

 acid, only shows, besides an extremely intense continuous spectrum which occupies 

 the whole visible portion up to about 3300, the four following triplets : 



* According to the determination of M. HASSELBERG. 

 . t According to determinations by MM. EXNER and HASCHEK. 



| This triplet and the following are probably two terms of a series ; in fact, their appearances in the 



flame spectrum arc identical. Moreover, the differences between the wave numbers ( - I of the first two 



\*/ 



lines of each of them are respectively 82 and 92, and between the wave numbers of the second and the 

 third lines, 112 and 114 respectively. 



SUMMARY OF RESULTS. 



An inspection of the preceding tables will have shown that the lines in the spectra 

 produced under the conditions of my experiments are much more numerous than is 

 the case when the salt spray is not previously mixed with the gases which react to 

 form the flame, but is introduced in some other manner. In the latter case it does 

 not really enter into that zone of flame where the most intense chemical reactions are 

 occurring and where the temperature is most elevated. Two different causes might 

 be suggested in order to explain this increase in the number of the lines. 



The flame is divided into two quite distinct portions : an inner one which is reducing 

 in its action, and another one which is oxidizing on account of the presence of air in 

 excess. In the working of the sprayer the metallic salt is forced to pass in succession 

 through these two regions, i.e., from the reducing region to the oxidizing region. It 

 is possible that, during the passage across the boundary separating these two regions, 

 there is a period, possibly very short, in which the metal, liberated from its 

 combination, exists in the state of metallic vapour. The atom is at this moment in 

 the hottest portion of the flame, namely, that which surrounds the blue inner cone 



