1881.] Carbon, Hydrogen, <J*c, in Organic Compounds. 329 



which is generally represented in onr graphic formulae by two carbon 

 atoms linked by double bonds. 



The value assigned by Briihl in such cases is, however, 61. This 

 somewhat higher figure is deduced from the aggregate value of the 

 six carbon atoms in the nucleus of the aromatic series, which (except 

 in benzol and its simpler substitution products) would appear to be 

 nearer 37 than 36. If equally distributed over the six atoms this 

 would give a value of at least 6*1 for each. The fact, however, is 

 susceptible of another interpretation. It does not follow that in these 

 more complicated bodies all the carbon atoms are exerting the same 

 influence on the rays of light. The replacement of hydrogen by some 

 monad radicle is an important change ; and if that radicle be CH 3 it 

 is evident that according to present views the carbon atom must have 

 all four of its units of atomicity satisfied with carbon, and by analogy 

 we should expect it to have its refraction increased. What that in- 

 creased value may be, or which indeed of the two hypotheses is most 

 in accordance with the facts, it seems to me that we have not yet 

 sufficiently accurate data for determining. 



When a carbon atom has all four of its units of atomicity satisfied 

 by other carbon atoms, each of which has the higher value of 6*0 or 

 6*1, its equivalent of refraction is greatly raised. There are com- 

 pounds in which the atoms of carbon actually outnumber the atoms of 

 hydrogen or its substitute, such as naphthalene, C 10 H 8 (ref. eq. 75*1), 

 naphthol, C 10 H 8 O (79*5), phenanthrene, C 14 H 10 (108*3), and pyrene, 

 C 16 H 10 (126'1). That the refraction is greatly raised is evident from 

 the fact that, if we were to reckon all the carbon atoms at 6*1, the 

 refraction equivalent of the body would not be fully accounted for. It 

 is evident that in pyrene only ten of the atoms of carbon can be in the 

 same condition as they are in benzol or styrol, the other six must have 

 all their units of atomicity satisfied by carbon alone. Now, if we allow 

 6*0 as the value of each of the ten carbons, and 1*3 for each of the ten 

 hydrogens, we get 73*0, which taken from 126*1 leaves 53'1 for the 

 remaining six atoms of carbon, or 8 - 8 for each. By a similar calcula- 

 tion the four extra atoms in phenanthrene are found to have the value 

 of 8*8 each. Taking oxygen at 2*9, naphthol gives 9*1 for each. But 

 the experimental data do not indicate a higher value than 8*4 for each 

 of the extra carbon atoms in naphthalene. Provisionally I venture to 

 assign 8*8 as the refraction equivalent of this highest carbon. 



There are several other bodies, such as anthracene, anethol, furfurol, 

 and hydride of cinnamyl, which from their abnormally high refraction 

 appear to contain carbon in this last condition. 



Hydrogen. — The general evidence with regard to hydrogen in 

 organic compounds tends to show that it has only one refraction equi- 

 valent, that originally assigned to it by Landolt, 13. 



Oxygen. — Briihl has been the first to point out that oxrgen in organic 



'2b2 



