BAC WATER

Bacteriostatic water is a sterile aqueous solution containing a bacteriostatic preservative, commonly benzyl alcohol at 0.9 percent, supplied for controlled laboratory and research applications in 10 mL and 30 mL presentations. It is a prepared solution rather than a compound, and its role is as a diluent for lyophilized research materials. It is supplied strictly for laboratory research use and is not for human or veterinary use.

The difference from plain sterile water is the preservative. Benzyl alcohol is bacteriostatic rather than bactericidal: it suppresses the multiplication of bacteria introduced during handling rather than sterilising the contents on contact, which is what makes a container suitable for more than one withdrawal. Because the item is a solution of two components rather than a single molecular entity, no CAS registry number, molecular formula or molecular weight is catalogued for it, and none is stated here.

Two practical consequences follow from the organic co-solvent. The resulting solution is not pure water, so methods that assume a purely aqueous matrix have an additional component to account for, and compatibility with a given peptide or protein is a property of that material rather than of the diluent. The exact composition and the sterility claims for any lot are those stated on the manufacturer's labelling and certificate documentation.