We discuss multichain effects in salt-free polyampholyte solutions of
finite concentration and find that the existing single-chain theories
are limited to exponentially small concentrations, if the sample conta
ins chains with net charges of both signs. We show that charged polyam
pholytes have a strong tendency to form neutral complexes and to preci
pitate. Neutral samples, where the average net charge of the chains is
exactly zero, phase separate at exponentially small concentrations. T
he supernatant is dominated by neutral unimers or clusters that form s
pherical globules and its polymer concentration c(dil) similar to exp(
-(N) over tilde(2/3)) is independent of the total polymer concentratio
n. For non-neutral samples, on the other hand, the free counterions ac
cumulate in the supernatant together with the most strongly oppositely
charged unimers, if the system is concentrated beyond the onset of ph
ase separation. The dilute phase then consists of elongated globules a
nd has a concentration proportional to the total polymer concentration
.