Citric Acid Anhydrous Vs Monohydrate

Citric acid is available in two main forms: anhydrous and monohydrate. The key differences between them are:

Chemical Composition :

Anhydrous (C₆H₈O₇): Does not contain water molecules.
Monohydrate (C₆H₈O₇·H₂O): Contains one molecule of water per citric acid molecule.

Physical Properties:

Anhydrous: Appears as a fine white crystalline powder.
Monohydrate: Crystalline powder but slightly larger crystals due to the water content.

3. Molecular Weight:

4. Stability & Storage:

Anhydrous: Less stable at high temperatures, as it loses water and converts to the anhydrous form at ~40°C.
Monohydrate : More stable in dry conditions; preferred for moisture-sensitive applications.

5. Applications

Anhydrous: Preferred in formulations requiring low moisture content (e.g., dry blends, powders, effervescent tablets).Used in pharmaceutical, food, and cosmetic industries.
Monohydrate: Common in liquid formulations due to its slower dissolution rate.Used in syrups, beverages, and wet granulation processes.

6. Conversion :

If switching between forms in a formulation –

Pharmaceutical Applications

Tablet Formulations (Solid Dosage Forms):

Preferred: Citric Acid Anhydrous
Reason: It has lower moisture content, which prevents degradation of moisture-sensitive drugs and improves tablet stability.
Common use: Effervescent tablets, chewable tablets, and dry powder formulations.

Liquid Formulations (Syrups, Oral Solutions, Injectables):

Preferred: Citric Acid Monohydrate
Reason: It dissolves more gradually, which can help maintain stability in solutions.
Common use: pH adjustment in syrups, parenteral solutions, and ophthalmic products.

Wet Granulation Process: