The salt aqueous solution properties of a low charge density polyampholyte terpolymer with a balanced stoichiometry of charges were investigated by static and dynamic light scattering. At high ionic strength, the sample is entirely soluble and the chains exhibit an excluded volume conformation. When the salt content is lowered, part of the sample precipitates, leaving in the supernatant highly swollen chains. The results are interpreted by assuming that, due to different reactivity ratios of the monomers, there is a distribution of the net charges among the polymer chains. By varying the salt content, one performs a fractionation of the polyampholyte chains according to their net charge.