213 

 Polarization of Cadmium Cells. 



By R. R. Ramsay. 



This work is a continuation of some worlv reported at a previous meet 

 ing (Ind. Acad. Proc. 1909), in wliich it was shown tliat if a cadmium 

 cell was polarized it would regain its normal E. M. F., if the cell contained 

 niercurous sulphate, but' vy,p«ld X'emain polarized if the mercurous sulphate 

 was absent. In that pai)er it was stated that wlien the mercury from the 

 polarized cell was spai-ked, a spectroscope showed the cadmium lines. 

 Since then I have been able to obtain a photographic record of the fact, 

 which I present at this time. The photographs were made with a large 

 Hilger quartz spectograph using Cramer spectrum plates, which are 

 sensitive for the entire visible spectrum and far up into the ultra violet. 



The cadmium amalgam from the mercury terminal of the polarized 

 cell was placed in a small arc lamp made as follows: The lower terminal 

 was made of the amalgam in a quartz tube which had a heavy copper wire 

 leading into the bottom. Fireclay was used to make the tube mercury 

 tight around the wire. The upper terminal of the arc was a heavy copper 

 wire. After filling the cup with the amalgam the terminals were drawn 

 apart and an arc could be maintained for about 10 seconds, after which 

 it was necessary to fill the cup again with the amalgam. The current 

 strength was about three amperes. The arc was focused upon the slit of 

 the spectrograph by means of a quartz lens. The spectrum of the amal- 

 gam is shown, together with the spectrum of mercury taken with the same 

 fire lamp, the spectrum of cadmium arc between C. P. cadmium rods and 

 also the spectrum of an arc between copper terminals. Referring to the 

 plate beginning at the top : We have 1st, mercury arc of short exposure, 

 the brighter lines showing on the plate; 2d, the cadmium amalgam arc 

 made with three different lengths of slit, thus bringing out the fainter 

 lines and avoiding to some extent the blurring due to the brighter lines ; 

 3d, the spectrum of the cadmium arc, showing four lines in the visible 

 spectrum, which can be identified in the cadmium amalgam spectrum, to- 

 gether with a large number in the ultra violet; 4th, the spectrum of the 

 copper arc. The wave lengths of several of the more prominent lines are 

 marked. This will serve to give one an idea of the accuracy of the scale 

 as well as to identify the copper lines; 5th, the mercury arc of long ex- 

 posure; 6th, the cadmium amalgam arc, and, 7th, the cadmium arc. 



