68 



differ from it in thai I lie |)(>sitive luicleiis ot' potassium possesses 

 one unit of cluirge more. Like (lie arc-spectrum of argon, tlie spark- 

 spectrum of potassium must be composed of a great nuujber of 

 lines, and not show sei-ies. As yet the relation which the displace- 

 ment law renders probable, is only tpialitatively known. 



For some liuie some researciies have been in progress in the 

 Amsterdam laboratoi-y to determine the relation quantitatively. 



We will here commuuicale some lesults to which the investiga- 

 tion of potassinni has led. These facts retain their valne whatever 

 interpretation may have to be given to them. 



Besides the arc-spectiiim of potassium with the so well-known 

 spectrum series which according to Sommehfkld's opinion originates 

 from the neutral atom, Edkh and Valenta ^) observed in 1894 a 

 spectrum, emitted by ionized potassium, which was very rich in 

 lines. Eder and Valunta observed sininltaneously arc- and spark 

 lines; in 1907 Goldstkin ') however, succeeded in observing in the 

 intensely luminous line of dischai'ge occurring in the passage of vigor- 

 ous electric discharges thiough powdered salts, a spectrum in which 

 only lines ai'e seen which have not been ranged into series, and in 

 which even the distinct arc-lines did not appear. Goldstein points 

 out that these lines owe their origin to circumstances which differ 

 essentially from those which give rise to the arc-lines, and he 

 introduces the juime of "ground" spectrum. We are undoubtedly 

 justified in attributing the ground spectra to the emission of the 

 once ionized atom. 



In the subjoined Table I a * denotes the strongest lines, those 

 published by Goldstein. 



With better appliances Eder's pupil Schillinürr 'j could supple- 

 ment Goldstein's obsei-vations by investigating also the ultra-violet. 

 He worked with vigorous discharges between potassiuu) electrodes 

 in a bulb with hydrogen. His observations are given under S in 

 Table I. 



In 1915 some observations of Nelthorpe'') were published for 

 potassium lying between 6307 A and 3898 A. He employed 

 another type of tube than Goi-dstein, and recorded by means of a 

 specti'ograph. On his plates tlje arc-lines are absent, the ground- 

 spectrum of Goldstein coinciding with his strongest lines. The 

 doubt expressed by Kayser whether Goldstein's failure to see the 



1) Eder u. Valenta, Denkschriflen Wien. Akad. 61. 347, 1894. 



2) Goldstein, Verh. deutsch. physik. Ges. 321. 1907; 426, 1910. 

 ») ScHiLLiNGER, Wiener Sitz. Ber. 118 [2a] 605. 1909. 



*) Nelthorpe. Astroph. Journ. 41. 16. 1909. 



