486 



Royal Society : — 



Other homologous series of the same group, such as the iodides, 

 compound ethers, or mercury compounds, were also examined, and 

 they all agree in exhibiting a progressive change in refraction and 

 dispersion with the advancing members of the series ; but in which 

 direction and to what extent depend on the other substances with 

 which the compound radical is combined. Yet, if we regard not 

 the actual indices, but these, minus unity, divided by the density, a 

 pretty regular increase is found to take place as the series advance. 

 The following Tables exhibit this : — 



Specific Refractive Energy. 



Radical. 



o 



o 

 o 



< 



o 





Is 



a 

 1 



6 



<U 

 U 

 < 





O 



T3 



11 

 & a 



•1707 

 •2112 



« c 



11 



o 



t 



Methyle 



Ethyle 



Propyle 



Butyle 



C 2 H 3 



C 6 H 7 



C 16 H 17 



C U H 25 



•4105 



•4482 



•4895 

 •5096 



•2359 

 •2614 



•3213 



•3905 

 •4127 

 •4333 

 •4402 

 •4492 

 •4750 



•4890 



'3905 

 •4432 



•389 

 •4127 



•4527 



•4402 ,'3502 

 ■4724 «43nfi 



•3727 

 •3376 



•5499 

 •5522 



(Enanthyle . . . 



Capryle 



Laurostearyle 





... 



Specific Dispersion. 



Radical. 



Alcohol. 



Iodide. 



Ether of 

 Acid. 



Acetate. 



Mercury 

 Compd. 



Stannic 

 Compd. 



Hydride. 



Methyle 



163 

 190 



212 



237 



209 

 218 



224 



168 

 174 

 191 

 191 

 198 



174 



198 



140 

 170 



256 

 268 



241 

 237 



Ethyle 



Propvle 



Butyle 



Amyle 



(Enanthyle 



Capryle 





Other groups of homologous bodies were also examined. Benzole, 

 toluole, xylole, cumole, and cymole gave nearly the same numbers, 

 and no regular progression. Pyridine, picoline, lutidine, and collidine 

 showed an augmentation of the specific refractive energy, but a 

 diminution of the specific dispersion with the advancing series. 

 Chinoline and lepidine (which proved to be the most refractive 

 organic liquid known) showed an increase of each of the optical 

 properties by the addition of C 2 H 2 . Thus the influence of the 

 added increment on the rays of light differs in different groups, 

 just as it does in respect to the boiling-point. 



IV. The refraction, dispersion, and sensitiveness of isomeric 

 liquids. — Several of the liquids, isomeric with the different members 

 of the benzole series, were examined ; some proved to be identical in 

 all optical properties ; others sensibly the same in actual refraction 

 and dispersion, though slightly different in density ; some again 



