In this
method, the protein solution is dialyzed against a precipitant solution through a semi-permeable membrane. Dialysis trials are more cumbersome
to set up, but one advantage of dialysis is that precipitations conditions of low ionic strength can easily be tested. This is desirable if the protein is
poorly soluble at low salt concentrations, since the protein may then crystallize as the salt is dialyzed away from the protein buffer. A solid phase
(gel) can be used to control the rate of dialysis. For example, an agarose gel inside a capillary can be used as the diffusion interface between the
protein and precipitant solutions (Figure 1C).