A solvent for reconstitution
Bacteriostatic water is water that contains a small amount of benzyl alcohol (typically 0.9%), which inhibits the growth of bacteria and allows a vial to be accessed multiple times over a period of time. In peptide research it is one of the common solvents used to reconstitute a lyophilized (freeze-dried) peptide into solution so it can be handled in the lab.
How it differs from sterile water
Sterile water for injection contains no preservative and is generally intended for single use. Bacteriostatic water’s benzyl alcohol lets a multi-dose vial resist microbial growth between accesses. Dedicated reconstitution solutions are another option some labs prefer. This is a description of the material, not a use instruction — all handling here is for laboratory research only.