BP102T • Unit 4Topic 2 of 3⏱ 5 Min Read

2. Eutectic Mixtures & Effervescent Granules Stoichiometry

💡 Core Concept & Clinical Context:

A Eutectic Mixture is formed when two or more solid crystalline substances (such as Menthol, Camphor, Thymol, Phenol, or Aspirin), when mixed together at room temperature, experience a mutually lowered melting point below ambient room temperature, liquefying into an oily liquid. To dispense eutectic powders safely, an inert absorbent diluent (Light Magnesium Carbonate, Kaolin, Starch, or Talc) is incorporated to absorb the liquefied mixture. Effervescent granules consist of an API formulated with a stoichiometric blend of Citric Acid, Tartaric Acid, and Sodium Bicarbonate in the ratio of 1 : 2 : 3.4 by weight to liberate carbon dioxide ($CO_2$) upon contact with water, masking unpleasant bitter drug tastes.

Clinical Scenarios & Pharmacopoeial Examples:

1Stoichiometric Acid-Base Reaction in Effervescent Granules

Chemical balance for carbon dioxide liberation.

Step-by-Step Breakdown:

•1. Citric Acid Reaction:

•H3C6H5O7.H2O + 3 NaHCO3 -> Na3C6H5O7 + 4 H2O + 3 CO2 ^

•(1 mole Citric Acid reacts with 3 moles Sodium Bicarbonate)

•2. Tartaric Acid Reaction:

•H2C4H4O6 + 2 NaHCO3 -> Na2C4H4O6 + 2 H2O + 2 CO2 ^

•(1 mole Tartaric Acid reacts with 2 moles Sodium Bicarbonate)

•Ideal Industrial Weight Ratio:

•Citric Acid Monohydrate : Tartaric Acid : Sodium Bicarbonate = 1 : 2 : 3.4

📋Key Takeaways & Exam Highlights

Why both acids are used: Citric acid alone produces sticky, unmanageable granules; Tartaric acid alone produces chalky, friable granules that crumble. Combining them 1:2 gives ideal mechanical hardness and rapid effervescence.
Heat Fusion Method: The single molecule of crystallization water in Citric Acid Monohydrate ($H_3C_6H_5O_7\cdot H_2O$) is released at 93-104°C to form the granulating dough without adding external solvents.
Wet Granulation Method: Anhydrous ethanol is used as the moistening liquid to avoid premature effervescence.

🇮🇳 हिन्दी व्याख्या (2. Eutectic Mixtures & Effervescent Granules Stoichiometry)

मेन्थॉल और कपूर को आपस में मिलाने पर वे पिघलकर लिक्विड बन जाते हैं, इसे Eutectic Mixture कहते हैं। एफरवेसेंट ग्रेन्यूल्स में सिट्रिक एसिड, टार्टरिक एसिड और सोडियम बाइकार्बोनेट (1 : 2 : 3.4) पानी में डालते ही CO2 गैस छोड़ते हैं।