Leonard and Whelan — Quantitative Spectra of Lithium, fyc. 275 



necessity of making separate adjustments for portions of the spectrum of 

 widely different refrangibility. 



The spark was obtained from a Euhmkorff's Induction Coil with a current 

 of 5 amperes, a self-induction coil and condenser being placed in circuit. 



Small conical glass tubes were previously used to keep the solution Tinder 

 examination up to the level of the top of the electrodes. By making the 

 electrode of foil wrapped in the shape of a tube about 1 mm. bore, the glass 

 tubes were dispensed with. 



"Wratten and Wainwright's panchromatic plates were used throughout, 

 and it will be seen from the illustration how strongly the red hydrogen line at 

 A 6563 develops on these plates. The plates were developed with pyro-soda 

 in total darkness for three minutes. 



The lines were measured on a micrometer reading to towo °f an inch, 

 and identified by reference to a carefully prepared curve. 



Certain letters of the Greek alphabet have been used, as before, to denote 

 the relative persistency of the lines. 



Thus :— 



t = seen with the metal, not with strong solution. 

 <7 = seen with strong solution, not with 1% solution. 



<t> = „ 1 'o „ „ "1 /o 



■0l7o 

 ■0017c 



Gold electrodes were used in the first instance, and when in certain cases 

 solution lines were masked by coincidence with gold lin es, the exposures were 

 repeated, using copper electrodes. An attempt to use lead electrodes was 

 unsuccessful, as the lead was rapidly attacked by the hydrochloric acid 

 present, and gave a spectrum so dense as to render difficult the observation 

 of the lines due to the solution under examination. In the examination of 

 the lines given by gold solutions, platinum and silver electrodes were em- 

 ployed, the latter giving the more satisfactory results. 



Exposure — The exposures were one minute for the electrodes (long), and 

 two minutes for the solutions (short). 



Metallic Spark Spectra.— -The spectra of lithium and rubidium were 

 obtained by sparking the metals in an atmosphere of hydrogen in a glass 



SCIENT. PROC. E.D.S., VOL. XV., NO. XXV. 2 Y 



