Examination of unofficial liquid pharmaceutical speciality products
and similar official products indicates that a minimum of 15% alcohol is
required to preserve the product from microbial growth if no other preservative
agents are present. Industrial pharmacists usually regard 15% alcohol as
adequate for the preservation of products with a pH of 5, while 18% has
been considered adequate for neutral or slightly alkaline preparations.
It is obvious that products such as tinctures, spirits, and fluid extracts
possess alcohol in concentrations that far exceed these values and need
no further preservative.