CHEMICAL SUBSTANCES BY MEANS OF GENERIC RADICALS. 339 



prominently brought forward, and the vacancies, not yet filled np by experi- 

 ment, in the list of conceivable compounds, distinctly pointed out. 



The division of molecules into two parts, one more readily undergoing chemical 

 change than the other, presents certain analogies to the " Theory of Copulae," 

 proposed by Berzeltus. This is most marked in the case of the acids con- 

 taining (COHO)', and (S0 2 HO)'. On the theory of copulse, these acids contain 

 oxalic acid C 2 3 , H 2 0, or hyposulphuric acid S 2 5 , H 2 0, and a copula. Thus 

 acetic acid was considered as C 2 H 6 , C 2 3 , H 2 0, sulpho-benzolic acid as C 12 H 10 , 

 S 2 5 , H 2 0, &c. ; according to the view which is taken in this paper, acetic acid 

 contains the- h alf of C 2 H 6 (methyl), and the half of oxalic acid ; sulpho-benzolic 

 acid, the half of C 12 H 10 (phenyl), and the half of hyposulphuric acid. In the 

 same way, the older chemists regarded hydrochloric acid as H 2 C1 2 , a com- 

 pound of the molecule H 2 , with the molecule Cl 2 , while we now consider it as con- 

 taining the halves of these molecules. It is therefore as correct to say, that acetic 

 acid is a compound of methyl and oxalic acid, as that hydrochloric acid is a 

 compound of hydrogen and chlorine. To prevent confusion, it is however better, 

 whenever it can be done, to have separate names for the radical and the substance. 

 Thus we may call (COHO)' Carboxyl (as proposed by Bayer), and distinguish 

 it from (COHO) 2 oxalic acid, (S0 2 HO) / might be called Sulphoxyl, and thus be 

 distinguished from (S0 2 HO) 2 hyposulphuric acid. Even in the case of those 

 radicals whose names are the same as the isomeric substances, we may, in some 

 instances, make the distinction ; thus (CH 3 )' is methyl, (CH 3 ) 2 methyl gas, (CN)' 

 cyanogen, (CN) 2 cyanogen gas, CI' chlorine, Cl 2 chlorine gas. 



In conclusion, it may be interesting to enumerate some of those substances 

 which consist entirely of generic radicals — all of whose reactions are therefore 

 generic reactions — thus we have cyanogen gas (CN) 2 , consisting of two atoms of 

 the generic radical of the nitriles united together ; glyoxal (COH) 2 ; glycol 

 (CH 2 HO) „ or (©H) 2 ; oxalic acid (COHO) 2 , or H 2 ; hyposulphuric acid (S0 2 HO) 2 , or 

 2 2 , ; tartaric acid (probably) (CH(HO)) a (COHO) 2 , or (93), ; glycolic acid (CH 2 H0) 

 (COHO), or (®H)S; glyoxylic acid (COH) (COHO), or (COH)E; tartronic acid 

 CH(HO) (COHO) 2 , or©H 2 ; glycerine (probably) (CH 2 HO) 2 (CH(HO)), or® (©H) 2 ; 

 glyceric acid (CH 2 HO) (CH(HO)) (COHO), or (©H) {39) ; mesoxalic acid (CO) 

 (COHO) 2 , or COH 2 . 



VOL. XXIV. PART II. 4 Y 



