This section is from the "A Handbook of Useful Drugs" book, by State Medical Examining and Licensing Boards.
An aqueous solution, containing about 10 per cent, by weight of ammonia (NH3). On standing, this solution loses ammonia and hence should be kept in well-stoppered bottles and should frequently be tested by the pharmacist to insure its complying with the pharmacopeial requirements. Ammonia water is a colorless liquid, having a very pungent, characteristic odor and a caustic, soapy taste. It is freely miscible with water and alcohol.
Ammonia water is used chiefly for counterirritation in the form of: