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compounds have their analogues amongst the derivatives of tere- 

 phthalic acid. Terephthalic acid being a bibasic acid, maintains its 

 character throughout its various transformations, and it is this fact 

 which claims particular interest. 



Terephthalic acid, as well as its derivatives, forms the first term of 

 a new series of well-characterized bodies, and may, as such, be con- 

 sidered the prototype of a great number of compounds still unknown. 



Without dwelling at present on the tedious process by which 

 terephthalic acid is produced, we may mention that it is obtainable 

 from various sources. We have, for instance, found that it is in- 

 variably formed, in a relatively small proportion, when toluylic acid 

 is prepared from cymol ; it is also formed when cymol is treated 

 with fuming nitric acid for the purpose of preparing nitrotoluylic 

 acid. It is important to mention, that whether the cymol be pre- 

 pared from oil of cumin or from camphor, the result is the same. 



Subsequently, we found that insolinic acid, which was described 

 some years ago by Hofrnann as a new acid of the formula C 9 H 8 O 4 , 

 is in reality terephthalic acid. The formation of this acid from 

 oil of cumin or cuminic aldehyde by the action of chromic acid 

 on these substances, turned out to be the most ready method of 

 preparing terephthalic acid ; and the principal part of our experi- 

 ments were made with terephthalic acid which had been obtained 

 from oil of cumin by this process. 



Terephthalic acid being isomeric with phthalic acid, has the 

 formula C 8 H G O l (Carbon=12, Oxygen=16), as already known. 

 When pure, it forms a white opake powder ; but if thrown down 

 from a boiling dilute alkaline solution, it may be obtained in a 

 crystalline state. When collected on a filter, these crystals dry in 

 paper-like masses of a silky lustre. Terephthalic acid is not per- 

 ceptibly soluble in ether, chloroform, acetic acid, water, or the other 

 usual solvents. Concentrated sulphuric acid dissolves it to a con- 

 siderable extent, especially when warm, without the formation of 

 sulpho-terephthalic acid, and the acid separates unchanged on the 

 addition of water. On heating, terephthalic acid sublimes without 

 previously fusing. The sublimate, which is indistinctly crystalline, 

 has the same composition and properties as the original acid, and 

 therefore, unlike other bibasic acids, terephthalic acid cannot be 

 converted into an anhydrite by merely heating it. Terephthalic 



