Pharmaceutical Waters

The USPXVII recognizes as official the four solvent waters and the aromatic or medicated waters.

1. Water USP
   Water USP is hydrogen monoxide (H₂O), is a clear, colorless liquid practically colorless and tasteless. In pharmacy it is used as solvent as in the extraction of vegetable drugs and in the manufacture of few preparations used externally; as precipitating agent or for the purification of certain water insoluble products.
   Water or aqueous liquids are incompatible with alcoholic solutions as or instance when alcohol is used as solvent for many substances, such as free alkaloid, organic acids, volatile oils, or resins. Addition of water or aqueous liquids will cause partial or complete precipitation of the dissolved substances.
   
   
2. Purified Water, USP, BP, Ph.I.
   Purified water is a water purified by distillation or ion-exchange treatment. It is a colorless, clear liquid, without odor or taste. It is prepared by distilling 1000 volumes of water from a suitable apparatus provided with a block-tin as glass condenser. The first 100 volumes is collected and rejected as this contain foreign volatile substances found in ordinary water. The 750 volumes been rinsed with steam or hot distilled water immediately before being filled. And the rest is left as residue in the still which contains concentrated dissolved solids.
   Purified water is used in compounding sterile preparations applied externally specially for intended for open wounds, in general for collyria and dermatological preparations. Purified water is also used for official test and assay and in general for compounding the majority of pharmaceutical preparation. As for instance when Water USP is used instead of Purified Water USP to prepare Dilute Alcohol, the resulting solution may be turbid or may contain precipitate of insoluble calcium and magnesium.
   
   
3. Water for Injection USP
   Water for injection is a clear, colorless, odorless, liquid purified by distillation and contains no added substance.
   Important to Know: Water for Injection is used as a solvent for the preparation of parenteral solutions. Water for Injection should be rendered sterile and thereafter protected from bacterial contamination if parenteral solutions are prepared under aseptic conditions and are not sterilized by appropriate filtration in the final container.
   
   
4. Sterile Water for Injection USP, BP, Ph.I.
   Sterile water for injection is also known as Aqua pro Injectione, Water for Parenteral. It is a clear, colorless, odorless liquid sterilized and suitably packaged, contains no bacteriostatic agent.
   Sterile Water for Injection is used for the preparation of all aqueous parenteral solution including those used for animal assay.