Which of the following is NOT listed as a cosolvent for tinctures?

• A. Water
• B. Vinegar
• C. Glycerol
• D. Propylene Glycol

Answer: (A)

Cosolvents are added to the primary solvent in tinctures to adjust polarity and improve the solubility of constituents that have different solvent affinities. Tinctures are typically alcohol (ethanol) based, and formulators use glycerol (glycerin), propylene glycol, or even vinegar as additional solvents to help dissolve both polar and nonpolar components and to tailor properties like taste and viscosity. Water, on the other hand, is not treated as a separate cosolvent in this context because the tincture’s solvent system is already hydroalcoholic; adding water would simply dilute the ethanol and does not provide the same targeted solubility benefits that the other cosolvents offer.