I. On the spectra of ignited gases and vapours, with especial regard to the different spectra of the same elementary gaseous substance

Abstract

1. In order to obtain the spectra of all the elementary bodies, you may make use either of flame or the electric current. For this purpose flame is preferable on account of its easy management, and therefore was immediately introduced into the laboratory of the chemist. But its use is rather limited, the metals of alkalies being nearly the only substances which, if introduced into flame, give spectra exhibiting well-defined bright lines. In the case of the greater number of elementary substances the temperature of flame, even if alimented by oxygen instead of air, is too low. Either these substances are not reduced into vapour by means of flame, or, if reduced, the vapour does not reach the temperature necessary to render it luminous in such a degree that by prismatic analysis we obtain its characteristic rays. The electric current, the heating power of which may be indefinitely increased by increasing its intensity, is alone fitted to produce the peculiar spectra of all elementary bodies. 2. In applying the electric current we may proceed in two ways. In one mode of proceeding the substance to be examined by its spectrum is at the same time, by means of the current, transformed into vapour and rendered luminous. In the other mode the substance is either in the gaseous state, or, if not, has been converted into it by means of a lamp, and the electric current ignites the substance in passing through.