Background and Objectives: Due to the volatility of alcohol, the concentration remaining of 70% alcohol after open is uncertain. To ensure that the solution is appropriate for use, it is necessary to test the stability of the prepared products after open and an expiry date can be determined.

Materials and Methods: The chemical stability study was an experimental design and conducted at the Faculty of Pharmacy, Srinakharinwirot University. By using gas chromatography, the samples were analyzed for concentrations of alcohol in forceps jars (I) for 7 days period, in cotton jars (II) for 7 days period, in opened bottles (III) for 60 days period and in unopened bottles (IV) for 360 days period, at room temperature and ambient temperature.

Results: The concentrations of alcohol remaining in (II), (III) and (IV), at room temperature and ambient temperature, on days studying were greater than 90 percent. Except, the concentrations of (I) at room temperature on day 7 and at ambient temperature on days 3 and 7, were less than 90 percent.

Conclusions: The seventy percent alcohol was stable at least for 7 days in cotton jars, at least for 60 days in opened bottles and at least for 360 days in unopened bottles when stored at either room temperature or ambient temperature. The seventy percent alcohol in forceps jars was stable at least for 3 days when stored at room temperature and at least for 2 days when stored at ambient temperature.

Keywords: chemical stability, 70% alcohol