ON THE STATE OF ORGANIC CHEMISTRY. 15 



of these formulae are rare. Tartronic acid, C 3 H 4 O 3 (w=3, x=0), illustrates 

 formula 9 ; orsellic acid, C 3 H* O l (w=8, x=2), formula 10 ; mesoxalic acid, 

 C 3 H 2 O 5 (n=3,#=0), formula 11 ; and aconitic acid, C° H° O 6 (w=6, x=l) 

 and chelidonic acid, C 7 H 4 G (w = 7, x=3), formula 12. 



By comparing these twelve formulae, it will be seen that 2 and 3 differ 

 from 1 by containing respectively one and two atoms more oxygen, and that 

 the same relation also exists among 4, 5, and 6 ; among 7, 8, and 9 ; and 

 among 10, 11, and 12 ; and further, that 4, 7, and 11 respectively differ from 

 1 by the substitution of O for H 2 , of O 2 for H 4 , and of O 3 for H e , and that 

 the same relations are repeated among 2, 5, 8 and 11, and among 3, 6, 9 

 and 12. That is, the substances represented by the formulae in the second, 

 third, and fourth columns are oxygen substitution-products of the substances 

 represented by the formulae in the first column, and of these latter substances, 

 the second and third are formed from the first by direct oxidation. Hence 

 all the twelve members of the group are genetically connected with the first 

 member. Comparing the chemical function of each with its composition and 

 corresponding place in the group, we see that the formulae in the top line re- 

 present monatomic compounds, those in the second line diatomic compounds, 

 and those in the third line triatomic compounds. Formula 1 represents mon- 

 atomic alcohols, and 4, 7, and 10 monobasic acids ; formula 2 represents di- 

 atomic alcohols, and 5, 8, and 11, diatomic* or bibasic acids; formula 3 

 represents triatomic alcohols, and 6, 9, and 12 triatomic or terbasic acids. 



From these considerations it will easily be seen how such a group might 

 be extended so as to include tetratomic compounds, or substances in which 

 more than six atoms hydrogen are replaced by oxygen. Such substances are 

 hitherto so rare, that it does not seem worth while to complicate the general 

 scheme of a chemical group by including their formulae. Instances of both 

 classes of compounds are, however, already known. Of the former class 

 (tetratomic compounds), the following substances (which arrange themselves 

 around an imaginary tetratomic alcohol, C H 4 O 4 (n=l, x=0), containing 

 the radicle (C)' v ), are examples: — bichloride of carbon, C CI 4 , and Hofmann's 



(C 8 H 5 ) 3 ) 

 cyantriphenyldiaminef, C 19 H 17 N 3 = H 2 I N 3 , obtained by its action on 



(cy J 



phenylamine ; also, in a certain sense, all cyanogen compounds, and therefore 



(C c H 5 ) 2 ] 

 such substances as melaniline, C 13 H" N 3 = H 3 I N 3 . Debus's glyco- 



(C) iv J 



(C 2 H 2 )'"] 

 sine}, C° H c N'=(C 2 H 2 ) iT i- N 4 , may be regarded as a tertiary tetramine de- 



(C 2 H 2 ) W J 

 rived from another unknown tetratomic alcohol, C 2 H° O 4 (w=2, w=0), 

 homologous with the foregoing. Several saccharine substances, for instance, 



* Acids may be diatomic, or even triatomic, while in a strict sense they are monobasic. 

 The acids of the glycolic series illustrate this distinction. These acids are monobasic; for 

 they contain only one atom of hydrogen which is replaceable by metals ; but at the same 

 time they are diatomic, for they form acid amides (glycocol, &c), chlorides containing CI 2 , 

 and intermediate chlorohydrates containing 1 atom chlorine. As Kekule has pointed out 

 (Lehrbuch d. organ. Chemie, 1859, p. 130), they are precisely intermediate in respect of 

 basicity (as well as of composition) between the glycols and the acids of the oxalic series. 

 Thus, glycol easily exchanges two atoms of hydrogen for acid-radicles, glycolic acid ex- 

 changes one atom of hydrogen for acid-radicles (formation of benzoglycolic acid) and one 

 atom for metals, while oxalic acid exchanges two atoms of hydrogen for metals, but none at 

 all for acid-radicles. 



t Hofmann, Proc. Roy. Soc. ix. 284. J Debus, ibid. 297. 



