No. Bacteriostatic water contains no salt. Its only ingredients are WFI-grade water and 0.9% benzyl alcohol as a preservative. The confusion comes from a different product with a similar name, bacteriostatic sodium chloride (often called bacteriostatic saline), which contains 0.9% sodium chloride and 0.9% benzyl alcohol. The two are not interchangeable.
How to tell them apart on the label
- Bacteriostatic water: the label reads “Bacteriostatic Water” and lists benzyl alcohol 0.9% (9 mg/mL) as the only additive. No sodium chloride appears anywhere on the label.
- Bacteriostatic sodium chloride: the label reads “Bacteriostatic 0.9% Sodium Chloride” and lists sodium chloride 9 mg/mL together with benzyl alcohol 9 mg/mL.
Both come in similar small vials with similar caps, so the product name and composition line on the label are checked at receiving and again before each use. See how to inspect a vial.
Why the difference matters in the laboratory
Because bacteriostatic water contains no dissolved salts, it has a conductivity close to that of purified water and adds no sodium or chloride ions to anything prepared with it. That matters wherever ionic strength, conductivity or chloride content is measured or controlled. Bacteriostatic saline, by contrast, contributes about 154 mmol/L each of sodium and chloride ions (9 g/L of NaCl divided by its molar mass of 58.44 g/mol). Its osmolality is roughly 300 mOsm/kg, whereas bacteriostatic water is close to zero. Neither product is buffered: bacteriostatic water has a pH of 4.5 to 7.0. See the pH of bacteriostatic water.
Related
Bacteriostatic water vs. bacteriostatic saline · Bacteriostatic water vs. sterile saline · What is bacteriostatic water?
All BAC Water Supply products are supplied for laboratory research use only and are not for human or veterinary use.