Dr. Hofmann on Insolinic Acid. 147 



These two series of acids are connected by the closest ties, and very 

 conclusive experiments have demonstrated that the members of the 

 former may be easily converted into those of the latter ; such is the 

 case of the transformation of butyric into succinic acid, effected by 

 M. Dessaignes under the influence of oxidizing agents. 



The following table exhibits these two series of acids arranged 

 according to their carbon : — 



Formic acid Cg Hg O4 



Acetic acid C4 H4 O4 



Propionic acid C^. Hg O4 ;. 



Butyric acid Cg Hg O4 



Valeric acid Cjq Hj^ O4 



Caproic acid 0^2 Hjg O4 



CEnanthylic acid C^^ ^u^a 



Caprylic acid C^g Hjg O4 



Pelargonic acid Cjg Hjg O4 



Rutic acid Cgo Hgo O4 



Oxalic acid C4 Hg Og 



}, •■: C, H, O^ 



Succinic acid Cg Hg Og 



Pyrotartaric acid Cj^ Hg Og 



Adipic acid . ^ Cjg Hj^ Og 



Pimelic acid 0^4 Hjg Og • 



Suberic acid Cjg Hj4 Og 



• ^18 H16 Og 



Sebacic acid C20 H^g Og - * 



The existence and the mode of formation of insolinic acid prove 

 that to the series of monobasic aromatic acids, Cn2^n2-%^^i the 

 lowest known term of which is benzoic acid, there corresponds 

 likewise a series of bibasic acids, 0^2 ^^2-8-2 08 = 0^2 H„2- 10 Og. 

 Of this series few members are at present known, but the group of 

 aromatic acids is itself very imperfect and limited. The two series 

 comprise at present the following terms : — 



Benzoic acid 0^4 Hg O4 



Toluylic acid Cjg Hg O4 



•. •• :• OigHi^04 



Cummic acid Cgo Hjo O4 



? C14H4O. 



j O16 Hg Og 



Terephthalic acid . , 



Phthalic acid , 



Insolinic acid C^g Hg Og 



'? O20 Hjo Og 



If we take the carbon as the standard of comparison, it is evident 

 that the bibasic insolinic acid corresponds to the monobasic acid, 

 which stands between toluylic and cuminic acid. In addition to this 

 unknown acid, toluylic acid only is represented in the series of bibasic 

 acids. There are, in fact, two bodies which may be regarded as 

 representatives of toluylic acid, namely, phthalic and terephthalic 

 acids. Benzoic and cuminic acid are not yet represented. 



