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XIV. Researches on Spectrum Photography in relation to New Methods of Quantitative 
Chemical Analysis. — Part II. 
By W. N. Hartley, F.R.S.E., &c., Professor of Chemistry, Royal College of Science, 
Dublin. 
Communicated by Professor Stokes, Sec. R.S. 
Received February 28—Read March 13, 1884. 
[Plates 15, 16.] 
Introduction. 
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.B.S., in the year 1862 (Phil. 
Trans., Yol. 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 Boyal Mint. In 1870 M. Janssen proposed two methods 
of quantitative spectrum analysis. The first was based on measurements of the in¬ 
tensity 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, lxxvi., 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 Bendus, lxxvi., pp. 707-711). In 1874 Messrs. Lockyer and Boberts 
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 estima¬ 
tion 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 fur 
