366 UVITIC ACID* 



in crystalline form on cooling ; sublimes undecomposed 

 without previously melting. 



Calcium terephtalate, C 8 H 4 4 Ca + 3H 2 0, and 

 Barium terephtalate, C 8 H 4 4 Ba + 4H 2 0, are crys- 

 talline compounds, very difficultly soluble in water/ 



Methyl terephtalate, C 6 H 4 (CO.O.CH 3 ) 2 . Long 

 prisms, fusing at 140, and subliming without decom- 

 position ; but slightly soluble in cold alcohol, easily 

 soluble in hot alcohol. The ethyl ether crystallizes in 

 prisms that fuse at 44. 



Nitroterephtalic acid, C 6 IP(N0 2 )(CO.OH) 2 . Is 

 formed by boiling terephtalic acid with very concen- 

 trated nitric acid. Cauliflower-like masses ; fusing 

 point, 259 ; moderately easily soluble in water. 



Sulphoterephtalic acid, C 6 H 3 (S0 2 .OH)(CO.OH) 2 , is 

 formed by heating terephtalic acid with fuming sul- 

 phuric acid in sealed tubes for six hours. The barium 

 salt can be purified by recrystallization. 



Hydroterephtalic acid, C 8 H 8 4 , is formed by the 

 action of nascent hydrogen (sodium-amalgam) on 

 terephtalic acid in a strongly alkaline solution. 

 "White powder, very similar to terephtalic acid. 



2. Acids, OTBTO 4 = C 6 H 3 J 



1. Uvitic acid (1:3: 5). Is produced, together 

 with mesitylenic acid (p. 340) by continued boiling of 

 mesitylene with dilute nitric acid ; and by boiling pyro- 

 racemic acid (p. 175) with barium hydroxide. Color- 

 less, fine needles; fusing point, 287 ; almost insoluble 

 in cold water, difficultly soluble in hot water, easily 

 soluble in ether and alcohol ; not volatile with water 

 vapor; when oxidized with chromic acid, it is con- 

 verted into trimesic acid, and, when heated with an 



