Initially you dissolved all, or most, of the p-aminobenzoic acid in ethanol. then you slowly added sulfuric acid. as you did this, a large amount of white solid formed. during the course of the reaction, that white solid dissolved. what was that white solid that formed upon addition of sulfuric acid?

This reaction is known as esterification, esterification is done by reacting carboxylic acid with alcohol in the presence of acid. Below reactions depicts the formation of ester (right reaction) and a formation of salt (left) this salt formed is insoluble in ethanol, hence, white precipitates are observed.