Spectrochemical Analysis * in Communication Research 



By BEVERLY L. CLARKE and A. E. RUEHLE 



The development of spectroscopy is traced through Newton, 

 Fraunhofer and Kirchoff to Hartley, Pollock and Leonard, and De 

 Gramont who, in the period 1880-1920, applied the spectroscope to 

 chemical analysis. It is shown that modern quantitative spectro- 

 chemical analysis began with the comparison standard method of 

 Meggers in 1922, and developments since that time are discussed. 

 The organization and functioning of the spectrochemical unit of the 

 analytical group at the Bell Telephone Laboratories is described, 

 and a number of examples of applications to telephone problems are 

 given. 



The foundation of spectroscopy may be traced back to the year 1666 

 when Sir Isaac Newton discovered that sunlight is composed of the 

 several colors, and that it could be separated into its components by 

 refraction with a prism. Newton failed to note the discontinuous 

 nature of the solar spectrum and it was reserved for Fraunhofer, more 

 than a century later, to investigate the absorption lines and to point 

 out their importance. Fraunhofer noticed that the D line absorption 

 doublet in the solar spectrum was identical in position with the bright 

 line doublet observed in a flame fed with sodium chloride. Finally in 

 1859 KirchholT formulated the modern concept of the composition of 

 the sun based on the observed absorption lines in the solar spectrum. 



As a result of Kirchhoff's theory much attention was at once turned 

 to the examination and mapping of the emission spectra of terrestrial 

 substances and testing for their presence in the solar atmosphere. 

 Bunsen and KirchhofT proved the presence of many terrestrial elements 

 in the sun. Lockyer actually discovered one element, helium, in the 

 sun almost thirty years before its discovery on the earth. Thus did 

 qualitative spectral analysis enjoy a brilliant beginning. 



In the years that followed Kirchhoff's work the spectroscope was 

 properly credited with many triumphs in the field of physics, but appli- 

 cations to chemical analysis were extended very little beyond simple 

 qualitative detection of the elements. In 1882, however, Hartley 

 performed quantitative analyses by determining at what concentra- 

 tions in solutions the various spectral lines of metals would disappear. 



* Any process of chemical analysis by means of the emission spectrum will be 

 called "spectrochemical analysis" in this paper. Absorption and fluorescence 

 methods have also been used but these will not be considered here. 



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