Density and Refraction of Gaseous Elements. 271 



Compounds. 



I. 



II. 



III. 



IV. 



V. 





Sub- 



Eefraction. 



Density. 



Sp. Eef. 



Eatio of 

 Eefraction 



Remarks. 



stance. 



|»-1. 



d. 



to that of 











d 



Hydrogen. 





N 2 0. 



E 2975 



E 19433 



15309 



2-14 



1 





1-47349 



28554 



18495 



33141 





NO. 



E 5159 



E 13254 



38924 



3-72 







71257 



12235 



59022 



33141 



| All these are calculated from 



CO. 



E 3350 



E 12179 



22947 



3-27 



[ experimental data of both 





52504 



29024 



36720 



57049 



index and density from 

 Prof. Everett. 



SO, 



E 7036 



E 26990 



26070 



507 







84733 



43120 



41613 



70525 





Cy. 



E 8216 



E 22990 



35737 



5-92 







91466 



36154 



55312 



77258 



t 



NH 3 . 



385 



0-761 





2-78 



\ 





5855 



8814 



7041 



4434 



6505 



HC1. 



449 



1-64 





3-24 



Calculated from Lup- 

 f 3969 ton's numbers. 





6522 



2148 



4484 



5107 



H 2 S. 



665 



1-52 





4-79 







8228 



1818 



6410 



6807 



; 



CH V 



443 



Calc. 





2-02 



\ 





6464 



8554 



7916 



3040 



Density calculated from hy- 

 drogen and equivalent. 



C a H 4 . 



678 



Calc. 





4-9 







8312 



8554 



7328 



6900 



; 



These to four places are evidently of less value than those above. 



Note by Prof. A. W. Eucker, F.R.S., on Mr. Dale's Paper. 



It has been shown that the volume of the molecules in unit 

 volume of the substance which they form is (fi 2 — l)/(/u, 2 -r 2), 

 where ft is the refractive index. 



If jju is nearly equal to unity (as in the case of the gases) 

 this expression reduces to § (fi — 1). Hence if B is the density 

 of the body, v and m the volume and mass of a molecule and 

 n the number of molecules in unit volume, 



M-i 



3 nv 

 2 nm 



2m c 



X2 



