NOTE ON THE SPECIFIC VOLUMES OF AROMATIC COMPOUNDS. 407 



Meyer's and Lü.schmidt's constants are, therefoi'e, only applicable 

 to benzene, ami not to its homologues with any strictness. 



I have calculated another value for carbon which, I admit, is as 

 arljitrarv as IMeyer's or Löschmidt's, but which has the merit of being 

 a{);)licable to aromatic hydro-carbons in general. I regard each of 

 the six atoms of carljon in benzene-nucleus as having the value 

 10. 5, while tlie hydrogen of the nucleus as well as the carbon and 

 hydrogen of the side-chains possess their normal values, viz. C=ll 

 and H=5.5. 



Tliis consideration is, of course, derived from the observation 

 tliat the replacement of hydrogen in benzene by C Hj, Co Hj, &c 

 causes the same increase in volume as in saturated fatty compounds. 



The following comparison will make the above statement clear, 

 the numbers under ' observed ' being those obtained by R. Schiff.* 

 Kopp's determinations of benzene, cymene, and naphthalene are also 

 added. The ten atoms of carbon, in the last hydrocarbon, consti- 

 tuting the two Ijenzene nuclei are each of them ret^arded as hav- 

 in"' the value 10.5. 



Kopp. 



Benzene CV, H,j 1)5.8 



TolufneC.H,. CH, — 



Xylene CJi;. (CH,), — 



Eihyl Ijenzene C^ H^. C.^ II5 • — 



X. projjyl benzene CgHj. Cg H;"... — 

 P. Ethyl toli:ene C, H^. CH3. C, H, — 



Mesitylene C, H,. (C lb,). — 



Cymene C^ H,. CH3. CgH;" 183.5 



Xaphthalene Q\o Hg 1-19.2 



•Annalen *äo,71. 



