EDTA has 4 carboxylic acid groups, so adding a lot of base would ionize these groups and make the molecule negatively charged. Since water is polar and charged molecules dissolve very well in water, the deprotonation of the acids would make it a lot more soluble. Solution EDTA has 4 carboxylic acid groups, so adding a lot of base would ionize these groups and make the molecule negatively charged. Since water is polar and charged molecules dissolve very well in water, the deprotonation of the acids would make it a lot more soluble..