( 289 ) 



tions, we first give the solubilities in water at 25^ of the tive 

 nitrophthalic acids, in parts per 100. 



«-nitrophtalic acid |9-nitrophthalic acid 



2.048 very soluble 

 symmetric nitroisophthalic acid 

 with water of crystallisation. Asymmetric nitroisophthalic acid 



0.157 ' 0.967 



Vicinal nitroisophthalic acid 

 0.216 



Quantitative nitration of phthalic acid. This was done with abso- 

 lute nitric acid. It appeared that it proceeded very slowly even at 

 30', and therefore the phthalic acid was left in contact with six 

 times the quantity of nitric acid for three weeks. After dilution 

 with water the acid was expelled by heating on a waterbath or else 

 evaporated over burnt lime. The solid residue was then reduced to 

 a fine powder and freed from the last traces of nitric acid by pro- 

 longed heating at 110^. As under the said circumstances the mono- 

 nitrophthalic acids are not nitrated any further, it could be ascer- 

 tained by titration whether all the phthalic acid had been converted 

 into the mononitro-acid ; the product had but a very slight yellow 

 colour so that a contamination could be quite neglected. Of the pro- 

 duct, now ready for analysis, different quantities were weighed and 

 each time introduced into 100 c.c. of water, and after adding an 

 excess of «-nitrophthalic acid they were placed in the shaking appa- 

 ratus. The amount of acid dissolved was determined by titration and 

 from these figures the content in ,j-acid was calculated by making 

 use of a table which had been constructed previously and in which 

 was indicated whrch j?-nitroacid contents correspond with a definite 

 titre of a solution so obtained. As the mean of four very concor- 

 dant observations it was found that in the nitration of phthalic acid 

 with absolute nitric acid at 30^ is formed : 



49.5 7o "" and SO-5 °/o <?-nitroplithalic acid. 



The quantitative nitration of isophthalic acid was done in the 

 same manner as that of phthalic acid ; here also, a few weeks were 

 required for the complete nitration at 30^. The contamination with 

 yellow impurities could again be quite neglected as a but very faintly 

 coloured nitration product was obtained. This nitration product so 

 obtained contains the anhydrous symmetrical nitroisophthalic acid, so 

 that in the solubility determinations by which its composition was deter- 

 mined the hydrated acid had to be employed as the anhydrous acid 

 takes up water but very slowly and has a greater solubility- The 



