Limit Test of Ammonium (NH₄⁺)(Inorganic Pharmaceutical Chemistry – Semester I)
Why This Practical Matters? After Chloride, Iron, Heavy Metals, Arsenic, Nitrate, Lead, and Boron, the Limit Test of Ammonium is an important impurity test asked in: ✔ Practical exams ✔ Viva questions ✔ Theory MCQs ✔ Competitive pharmacy exams Understanding this test also helps students link chemical reactions with visual observation, which examiners love. 🎯 Aim of the Practical To determine the amount of ammonium impurity present in a given pharmaceutical substance and ensure it is within the prescribed pharmacopoeial limit. 🧠 Principle (Easy to Remember) Ammonium salts, when treated with alkaline potassium mercuric iodide (Nessler’s reagent), produce a yellow to brown colored complex. 👉 Intensity of color ∝ amount of ammonium present The color produced by the test solution is compared with the standard solution. ⚗️ Reagents Required Nessler’s reagent Ammonium standard solution Alkaline medium (usually sodium hydroxide) Distilled water 🧪 Apparatus Nessler cylinders Measuring ...