The first attempt to apply the spectroscope to the quantitative analysis of alloys seems to have been made by the late Dr. W. A. Miller, F. R. S., in the year 1862 (Phil. Trans., Vol. 152, p. 883,1863, and Jour. Chem. Soc., vol. xvii., p. 82, 1864). By taking photographs of the spectra of alloys of gold and silver of different degrees of fineness he obviously sought to apply this method of working to the assaying of gold. He was at the time an assayer to the Royal Mint. In 1870 M. Janssen proposed two methods of quantitative spectrum analysis. The first was based on measurements of the intensity of the most brilliant rays emitted by incandescent matter, while the second depended upon the time during which a substance emits visible rays during complete volatilisation in a flame (Comptes Bendus, Ixxvi., pp. 711–713). MM. P. Champion and H. Pellet, and also M. Grenier, applied the former spectro-photometrical method with some degree of success to the estimation of alkalies (Comptes Rendus, lxxvi., pp. 707–711). In 1874 Messrs. Lockyer and Roberts attempted and accomplished with a considerable amount of accuracy the determination of the composition of certain tolerably homogeneous alloys of gold and silver, and of lead and cadmium, by means of the spark passed between metallic electrodes, and examined by the spectroscope. The spectrum of the alloy was compared with certain check pieces of known composition. Others who have attempted to make use of emission spectra for the purposes of quantitative analysis are Sir J. G. N. Alleyne, who in 1875 communicated a paper to the Iron and Steel Institute “On the estimation of small quantities of Phosphorus in Iron and Steel by Spectrum Analysis” (Journal of the Iron and Steel Institute, 1875, pp. 62–72), and H. Ballman, who attempted the quantitative estimation of lithium with the spectroscope by observing the degree of dilution of a solution which seemed to cause the extinction of the red line. This is theoretically constant, but practically it varies slightly (Zeitschrift für Analytische Chemie, vol. xiv., pp, 297–301; also Journal Chem. Soc., 1876, p. 550, Abstract). Messrs. Liveing and Dewar have published notes on quantitative spectroscopic experiments (Proc. Roy. Soc., vol. xxix., pp. 482–489). Observing the emission spectrum of sodium vapour, they sought to estimate the quantity of substance present in a given space by measuring the width of the sodium lines.
XIV. Researches on spectrum photography in relation to new methods of quantitative chemical analysis.—Part II