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phthalic acids only a rough approximation (b}^ Miller) was known, 

 whilst in the case of the mononitroisophthaUc acids it had yet to 

 be ascertained which isomers are formed there from. 



We commenced by preparing the five mononitro-acids derived 

 from phtaUc acid and isophthalic acid in a perfectly pure condition. 

 In the case of the a- and /j-nitrophthalic acids no difficulties were 

 encountered, as the directions of Miller, save a few unimportant 

 modifications, could be entirely followed. The acids were therefore 

 obtained by nitration of phthalic acid and separation of the isomers. 



The symmetric nitro-isopkthalic acid was prepared by nitration 

 of isophthalic acid. It crystallises with 1 mol. of H,0 and melts at 

 255 — 256^ whilst it is stated in the literature that it crystallises 

 with JVs ï^ol. of HjO and melts at 248\ At first we hoped that 

 the other two nitroisophthalic acids might be obtained from the 

 motherliquors of this acid. It was, therefore, necessary to obtain the 

 isophthalic acid in a perfectly pure condition, as otherwise it would 

 be doubtful whether the byproducts formed were really derived from 

 isophthalic acid. By oxidation of pure /?i-xylene (from Kahlbaum) an 

 isophthalic acid was obtained which still contained terephthalic acid 

 which could be removed by preparing the barium salts. 



The mothei-liquors of the symmetric nitro-isophthalic acid appeared, 

 however, to contain such a small quantity of the byproducts that 

 the preparation of the nitro-acids (1, 3, 2) and (1, 3, 4) was out of 

 the question. These were therefore, prepared as follows : 



Preparation of asymmetric nitro-isophthalic acid (1, 3, 4). On 

 cautious nitration of m-xylene at 0° with nitric acid of sp. gr. 1.48 

 a mixture is formed of mono- and dinitroxylene which still contains 

 unchanged 7?i-xylene. This, on distillation with water vapour, passes 

 over first and when drops of the distillate begin to sink to the 

 bottom of the receiver the latter is changed and the distillation is 

 continued until crystals of dinitroxylene become visible in the con- 

 denser. 100 gr. of xylenegave about 85 gr. of mononitroxylol (1, 3, 4). 



After rectification of this mononitroxylene (b. p. 238°) it was 

 oxidised in alkaline solution with a slight excess of permanganate ; 

 20 gr. yielded 12 a 13 gr. of acid which, however, consisted of a 

 mixture of nitrotoluylic acid and nitro-isophthalic which could be 

 separated by crystallisation from water. In this way, the as. nitro- 

 isophthalic acid was obtained with a melting point of 245°. In water 

 it is much more soluble than the symmetric acid, namely to the 

 extent of about 1 7o- ^t 25°. Unlike the symmetric acid, it crystal- 

 lises without water of crystallisation in small, fairly thick, plate-like 

 crystals. It is very readily soluble in hot water, alcohol and ether, 



