10 THE ROYAL SOCIETY OF CANADA 



V. Absorption Spectrum of Lead 



Up to the present nothing has been known of the spectral series 

 of lead. Hence it was thought the method of arc reversals spectra 

 might throw Hght on the subject. 



As in the case of aluminium the metal in granulated form, chemi- 

 cally pure, was used. Absorption bands were obtained fairly readily 

 and extended down well into the ultra violet. It is interesting to 

 note that absorption could be observed visually at A = 4058 A.U. 



In all, 19 reversals were obtained varying in type. It was found 

 possible to classify them as follows: 

 Narrow Absorptions. Diffuse Absorptions 



4058 A.U. 2833 A.U. 



2614 " 2400 " 



2247 " 2170 « 



2060 " 2015 " 



1973 " 1938 " 



1925 " 1911 " 



1900 « 

 Since the absorption spectra of thallium and aluminium showed 

 the same characteristics of narrow and diffuse absorptions it is possible 

 that the series of narrow absorptions found in lead may correspond to 

 that in thallium and aluminium, viz. v = (2,p2) — (m,s) and similarly 

 the difïuse absorptions to the series v= (2,p2) — (m,d'). Further work 

 will be necessary to confirm this. The reproductions of Plate III 

 show (a) the carbon arc spectrum, {h) the lead arc emission spectrum, 

 (c) the lead arc absorption spectrum, and {d) that of the lead spark, 



VI. Absorption Spectrum of Tin 



The results obtained from the absorption spectrum of lead 

 suggested similar work with tin for which nothing is known of spectral 

 series. Unfortunately, the results were too meagre to make any 

 prediction regarding series, since the only absorptions obtained were 

 narrow reversals at 2141 A.U., 2096 A.U. and 2058 A.U. It is possible 

 that these may belong to the same series but the other members have 

 yet to be found. 



The reproductions of Plate IV show {a) the spectrum of the carbon 

 arc, (6) that of the tin emission arc, (c) that of the tin absorption arc, 

 and {d) that of the tin spark in air. 



VII. The Absorption and Flame Spectra of Arsenic 



As a result of the extension of the work on electrical determina- 

 tion of resonance and ionizing potentials to the case of metallic 



