1 40 Dr. J. H. Gladstone. The Relation between the 



This information is given in the preceding table (pp. 136 139), 

 in which, for the sake of completeness the lines obtained from eliasite 

 are also shown. 



In most of the experimental work connected with this research, I 

 have been assisted by Mr. Shackleton, while Mr. Fowler is generally 

 responsible for the determination of wave-lengths in the less 

 refrangible part of the spectrum, and Mr. Baxandall for the reduc- 

 tion of the photographs. 



" The Relation between the Refraction of the Elements and 

 their Chemical Equivalents." By J. H. GLADSTONE, D.Sc., 

 F.R.S. Received June 3, 1896. 



This paper is intended to give a preliminary account of some 

 recent investigations into the specific refraction of the elements. 

 It may be conveniently divided into two distinct parts. The first 

 part is a revision and extension of the list of specific and atomic 

 refractions, which was first published in the ' Phil. Trans.' for 1870, 

 and was reprinted with modifications in a lecture given at the Royal 

 Institution in 1877. The second part is an amplification of some 

 deductions made in that lecture. 



PART I. The Specific and Atomic Refractions of the Elements. 



The following table contains the atomic weights, the specific refrac- 

 tions, and the atomic refractions of the elements as revised and 

 extended. For the atomic weights I have adopted the numbers 

 recently published by the American Chemical Society's Committee on 

 Atomic Weights ('J. Amer. Chem. Soc.,' vol. 17), revised up to 

 January, 1894. In regard to the specific refraction, advantage has 

 been taken of the work done in some departments of the inquiry 

 by Landolt, Haagen, Briihl, Topsoe and Christiansen, Mascart, 

 Becquerel, Kanonnikoff, Soret, Nasini, Grhira, Perrot, Tutton, Lord 

 Rayleigh, Edwards, and others, as well as many additional observa- 

 tions made by myself or by Mr. Hibbert. 



The atomic refraction is the product of the numbers in the two 



earlier columns, that is, it equals P-^-j , where P is the atomic 



weight, and fil/d is the specific refraction, that is, the refractivity 

 divided by the density. Of course, these are not generally deter- 

 mined by observations of the element itself, but are deduced from 

 those of its salts or other compounds. 



