1901.] 



and Melting Points to Atomic Mass. 



'11 



m = 35319 -0-2233W 2 



\m + 1 + (2 - 3""*) (0 • 1 143 + • 000625 W)} 2 



The factor (2 — 3 - "') corrects for the variations in the fractional parts 

 •of /x, referred to above. 



The first principal series are obtained by adding to m + 1 in the 

 -denominator the term 18 W 2 x 10 -7 . 



[A closer approximation is given when, in Rydberg's general formula, 



N 



we substitute 



n x = 35349 -0 -2233 W 2 ; N - 109675, 



.and 



/x = {l-19126 + 0-00103W + (0-04377 + 13W 2 xl0- 7 )(l-3 1 -^)}. 



These values give the second principal series of potassium, rubidium, 

 •and caesium. To obtain the first principal series, increase the value of 

 v> by 182 W 2 x 10~ 8 . The value of n x , which the above gives for 

 rubidium, is 2 7 '5 units too great. 



The wave-numbers (10 s A -1 ), calculated from this amended formula, 

 are compared with the observed values in the following tables : — 



Potassium. 





Second Series. 



First Series. 



m. 



Observed. 



Calculated. 



Differ- 

 ences. 



Observed. 



Calculated. 



Differ- 

 ences. 



1 



2 

 3 

 4 

 5 

 6 

 7 



*12984 -5 

 f 12980 -0 

 24700 -3 

 28997 -8 

 31068 -0 

 *32224 -0 



12983 -1 



24700 -5 

 27998 -4 

 31066 -8 

 32223-6 



-1-4 

 + 3-1 

 + 0-2 

 + 0-6 

 -1-2 

 -0-4 



*13041'5 

 f 13036 -6 

 24719 -0 

 29006 -3 

 31072 -7 

 *32225 '8 

 *32939 '5 

 *33408 '5 



13038 -0 



24718 -1 

 29006 -2 

 31070-9 

 32226 -0 

 32937 '9 

 33407-1 



-3-5 

 + 1-4 

 -0-9 

 -0-1 

 -1-8 

 + 0-2 

 -1-6 

 -1-4 



* Kayser and Kunge. 



f Lehmann, 'Ann. d. Physik,' vol. 5, p. 633, 1901. Unmarked lines observed 

 by the Author (Flame Spectra). 



