t)R A. CRUM BROWN ON ISOMERIC COMPOUNDS. 709 



former boils at +11°C, the latter is a gas not condensible by a cold of -18^C. 

 There is also a great difference between them as to solubility in water. They 

 cannot be metameric, as there are not two possible constitutional formulae for 

 C^HjCl. They are therefore absolutely isomeric. The same argument does not 

 hold in the case of any of the homologues of chloride of ethyl except chloride of 

 methyl. For there may be two formulae for the molecule CgH^Cl, two for 

 C4H9CI, three for C^H^^Cl, &c., without varying the mode of arrangement of the 

 carbon atoms inter se. 



3. Chloride of vinyl and chloracetene are undoubtedly different. They 

 resemble one another in nothing but composition and molecular weight. If we 

 exclude the possibility of the existence of diatomic carbon* in such a molecule, 

 there is only one constitutional formula to represent them both, 



© © 



I I 



©-(^-(^-© 



4. The constitutional formula of succinic acid is 



I I I I 



Op (^ (b ^ 

 © (5) 



Maleic and fumaric acids, each form succinic acid by the addition of two atoms 

 of hydrogen. And as both are dibasic, these two atoms of hydrogen cannot be 

 contained in either of the groups HO in succinic acid. They must therefore be 

 two of the hydrogen atoms directly combined with carbon. Now, there are two 

 conceivable constitutional formulae by which they could be represented, 



©-^ ® ^-(o) and (o)-^ (^ © ^©or®-^ ^ ^ r-© 



^ -(c)- -(e)- -(i)- -(c)- -> ^ -(iy -^ -^- -(^- ^ V _(^_ _(^_ A ^_ J 



(^o) (i) ^) (o) (^ (0) 



® (b b (b b 



* I do not intend to deny the possibility of this, but all we know of such " non-saturated" sub- 

 stances leads to the belief that the atomicity of the carbon radical Cn is reduced, not by one or more 

 of the carbon atoms becoming diatomic, but by the union of the carbon atoms taking place in the 

 way represented by the following graphic forraulis : — 



(C3)- = ^ -(^- -(c)-, (C3)- = (cy -(^- -0- or (i)- -(cy -<^-, (C3)- = (^- -(c)- -(c> 



or -CcV-(c)--©-, &c. 



