Section III., 1915 [237] Trans. R.S.C. 



On the Ultraviolet Spectrum of Elementary Silicon. 



By Professor J. C. McLennan, F.R.S. and Mr. Evan Edwards, 

 M.A., University of Toronto. 



(Read May Meeting, 1915). 



In the course of some work by the writers with a fluorite spectro- 

 graph on the ultraviolet spectrum of mercury, cadmium and zinc 

 their attention was drawn to a paper recently published by Sir William 

 Crookes^ on "The Spectrum of Elementary Silicon." In this paper 

 the wave-lengths in the spark spectrum of this element are given down 

 to A = 2,124-63 A.°U. As the only wave-length as yet published for 

 this element, shorter than this limiting one, is one recorded by Eder 

 and Valenta^ at A = 1,929-0 A.°U. it was thought that it might be well 

 to examine the spectrum in the region below A = 2,125 A.°U. This 

 has now been done and the present paper contains a list of the lines 

 which have been observed down to A = 1,842-2 A.°U. 



Sir William Crookes in his paper records that the elementary 

 silicon of the highest purity which he was able to obtain was supplied 

 to him by the Carborundum Company at Niagara Falls. He also 

 records that the three samples supplied by them to him gave on 

 analysis 99-56, 99-86 and 99-98 per cent, of silicon the impurities 

 being titanium, iron and aluminium. 



On account of these samples being so pure the writers applied to 

 the manager of the above-mentioned company for a few small pieces 

 and these were sent to us with the accompanying statement that they 

 were presumably of as high purity as those with which the observa- 

 tions of Sir William Crookes were made. 



Our experiments were made with these pieces of silicon and we 

 desire here to acknowledge our indebtedness to the Carborundum 

 Company for their kindness in the matter. 



In making the experiments the spark was obtained from the dis- 

 charge of two one gallon Leyden jars charged with a 10 inch induction 

 coil. A great many plates were taken with different pieces of the 

 silicon and seven of the best of these were carefully measured up to 

 arrive at the wave-lengths of the different lines which came out. 



1 Sir William Crookes. Proc. Roy. Soc. No. A. 621. Vol. 90. Aug., 1914, 

 p. 512. 



2 Eder and Valenta Atlas Typischer Spectren, Wien, 1911. 



