206 Dr. Gladstone on some Recent Determinations 



potassium in its compounds with CO has still other valencies. 

 There is also another difficulty; for if we determine the atomic 

 dispersion of nickel and iron on the same principle, it will 

 be found to be 4' 8 and 5*2 respectively for the interval 

 between the lines y and a*; these numbers are about one fifth 

 of the atomic refraction of the two metals given above, viz,, 

 24*1 and 26*5. But the ratio between the atomic dispersion 

 (y—a) and the refraction of the most dispersive elements 

 hitherto calculated, sulphur and phosphorus, is only about 

 one tenth. 



It seems more probable that the metals really retain their 

 ordinary valency, and that the excessive refraction and dis- 

 persion is to be sought rather in the peculiar arrangement of 

 the CO. In such compounds we may imagine the CO 

 playing a part similar to that of the CH 2 in ordinary organic 

 compounds, which may be increased or diminished in number 

 without altering the general type of the substance. In fact 

 I accept on optical grounds as well as chemical, the ring- 

 formulse indicated in Mond's lecture at the Roval Institution. 



NJ 



Fe 



0-0 



0=0/ \c=o 



\ / 0=0 



c c 



I" 11 



o o 



0=0 

 0=0 



In that case the molecular refraction due to each CO would 

 be, from the nickel compound about 11'9, and from the iron 

 compound about 11*3. 



Although the atomic dispersion of nickel or of iron has not 

 yet been definitely measured, it cannot greatly exceed 05 for 

 7— a. It is evident therefore from the figures for the disper- 

 sion, viz., Ni(CO) 4 =5'9, Fe(CO) 5 = 6'6, that the molecular 

 dispersion of each CO must be about the same in these two 

 compounds, \\z. 1*3, or thereabouts. 



II. Indium and Gallium. 



In 1885 I calculated the atomic refraction of indium and 

 gallium from determinations of the refraction of certain 

 alums made by M. Charles Soret. Very shortly afterwards 



* Proc. R. S. xlii. p. 401. 



