[ 229 ] 
XVIII. 
ON THE QUANTITATIVE SPECTRA OF BARIUM, STRON- 
TIUM, CALCIUM, MAGNESIUM, POTASSIUM, AND 
SODIUM. 
By JAMES H. POLLOK, D.S8c., anp A. G. G. LEONARD, A.R.C.S.I. 
[Puates XVIII., XIX.) 
[Read, Apri 28; Received for Publication, Aprit 26; Published, Juny 25, 1907.] 
INTRODUCTION. 
THESE spectra were taken after the manner devised by Professor 
W.N. Hartley,’ with the modifications described in our previous 
paper on the quantitative spectra of the iron and zine groups.’ 
Gold electrodes were used, with a Rihmkorff’s coil and condensed 
spark, a Hemsalech self-induction coil being employed for the 
removal of air-lines. A photograph was first taken of the elec- 
trodes alone, with a long slit; the slit was then shortened, and 
the solutions or metal sparked, the spectra of the various elements 
thus showing as short lines between the long lines of the gold 
electrodes. The second spectra can then be easily identified by 
reference to the dotted and numbered gold lines, the wave-lengths 
of which are given in a preliminary table. 
When possible a photograph was first taken of the metal, 
with the lines of the metal long, and those of the electrodes short, 
to see if there were any lines coincident with the gold lines. 
Solutions were used saturated with the chlorides, and also 
containing 10 per cent., 1 per cent., ‘1 per cent., ‘01 per cent., 
and ‘001 per cent. of the element. In the tables the degree 
of persistency of the lines is indicated by the following Greek 
letters :— 
7 seen with the metal, not with solutions. 
o 5 strong solutions, not with dilute solutions. 
o a 1°/, solutions, not with °1°/, solutions. 
x ” Wife ” » Ole ie 9 
PR es Cen Meni Mp6 DisggN?p) 
Ge At WOR 
After sparking the strong solutions, it was found that in many 
cases the electrodes alone gave quite strong spectra of the metal 
1 Phil. Trans. Roy. Soc., vol. clxxv.. 1884, Part i., pp. 49-62, Part ii., pp. 325-342. 
2 Proc. Roy. Dublin Soc., vol. xi., p. 217, 1907. 
SCIEN. PROC. R.D.S., VOL. XI., NO. XVIII. 2G 
