GO Messrs. Brainier and Watts on the 



a great increase of dispersion. It was pointed out some years 

 ago that the aromatic bodies have a great dispersive power*, 

 and that " dispersion, as well as refraction, increases very 

 rapidly with the number of atoms of carbon that are not com- 

 bined with at least two of hydrogen or their equivalent."! 

 Evidence of this is to be found both in the older and the more 

 recent researches, whether in this country or on the Continent, 

 and is always accumulating. Confining our attention to the 

 figures given in this paper, it will be observed that in cases 

 where the carbon is normal the specific dispersion is expressed 

 by low figures (the highest of which is, in fact, acetone, 

 *0207); while in the isomeric allylic alcohol, which has a 

 higher refraction, it rises at once to '0275. The essential oils 

 and their congeners, and such bodies as cresylic acetate, are 

 above *0300 ; while the purely aromatic compounds are all 

 above '0400. 



2nd. Where isomeric bodies have the same or nearly the 

 same specific refraction for the line A, they have the same 

 also for the line H. The apparent deviations from this rule I 

 am disposed to attribute to experimental error, and still more 

 to impurity of substance. It is clear that in many cases of 

 carbon compounds the presence of a differently constituted 

 body would reveal itself by its influence upon dispersion more 

 than upon refraction. 



VIII. On the Specific Volumes of Oxides. By Bohuslav 

 Brauner, Ph.D., and John I. Watts, Owens College%. 



THE researches of Persoz, Karsten, Filhol, Kopp, Schroder, 

 Lowig, Schafarik, Playfair and Joule, Baudrimont, Heim- 

 roth, and others have yielded a considerable supply of material 

 relating to the specific volumes of many bodies, especially to 

 those of the oxygen compounds ; and by aid of these results 

 many interesting theories can be conceived. It was, how- 

 ever, Kremer § who first pointed out the regularities which 

 the volumes of the oxides of the natural groups of elements 

 exhibit. But after the demonstration of the Periodic Law 

 by Mendel ejeff this question considerably developed in im- 

 portance, because the relations of the various members of 

 the natural groups to one another were made more strikingly 

 apparent. Mendelejeff himself || points out the regularities 

 which the specific volumes of the oxides exhibit in the different 

 groups of the system ; but he only followed this out in one 



* Journ. Chem. Soc. 1870. t Proc. Boy. Inst. March 1877. 



\ Communicated by the Authors. § Pogg. Ann. exxx. p. 77. 



|| Ann. Chem. Pkarm. Suppl. viii. p. 143 ; Chem. News, xl. p. 255, xli. 

 p. 49. 



