of ammonium fumarate to ammonium aspartate to produce the solid product the solution is acidified to promote precipitation of the aspartic acid crystals when the ph reaches the isoelectric point at slightly less than ph 3 the u03b2 carboxyl group is fully neutralized to the carboxylic acid form pk a u02dc 3 9 while the x carboxyl group remains in the anionic carboxylate form pk a u02dc 2 1 the amine group is fully associated as the cationic nh 3 pk u02dc 9 8 in this form the crystals are quite insoluble in water even with heating they can be solubilized via addition of alkali to a slurry in water producing an aqueous solution of sodium or other cation aspartate however thermal polymerization of this product is unsuccessful as the sodium counterions block the carboxylate groups from forming amide bonds with the amine groups aspartic acid is also soluble in relatively strong acids for example sulfuric or nitric acids added in equimolar amounts or in slight excess will quickly bring aspartic acid into aqueous solution particularly with mild heating in these solutions the aspartic acid is fully acidified with both of the carboxylic groups in the acidic cooh form and the amine positively charged as nh 3 in the absence of counterionic coo u2212 groups no crystal lattice.