Organic acids and process for preparing same

In a process for preparing a mixture of polycyclic, aromatic polycarboxylic acids carrying nuclear nitro groups that is soluble in a mixture consisting essentially of methyl ethyl ketone and ethanol but substantially insoluble in water which consists essentially in subjecting a slurry containing coal to reaction with aqueous nitric acid having a concentration of about 5 to about 90 percent at a temperature of about 15.degree. to about 200.degree. C. for about 0.5 to about 15 hours and mechanically separating the solids in the resulting slurry, the improvement which consists essentially in extracting said separated solids with a mixture consisting essentially of methyl ethyl ketone and ethanol in amounts sufficient to form an azeotropic mixture and then separating said methyl ethyl ketone and said ethanol from the extract to obtain said mixture of polycyclic, aromatic polycarboxylic acids.