🧪 Limit Test of Iron | Pharmaceutical Inorganic Chemistry Practical
🎯 Aim To perform the Limit Test of Iron (Fe³⁺ ions) as per Indian Pharmacopoeia (IP) standards. 🔬 Principle Iron reacts with thioglycolic acid in an alkaline medium to form a purple-colored complex . The intensity of this color is compared with that of a standard iron solution using Nessler cylinders. Reaction: F e 3 + + T h i o g l y c o l i c a c i d + N H 3 ⟶ P u r p l e C o m p l e x Fe^{3+} + Thioglycolic \, acid + NH_3 \; \longrightarrow \; Purple \, Complex F e 3 + + T hi o g l yco l i c a c i d + N H 3 ⟶ P u r pl e C o m pl e x 🧰 Requirements Sample solution (suspected iron impurity) Standard Iron solution (20 ppm Fe³⁺) Thioglycolic acid Ammonia solution Distilled water Nessler cylinders ⚗️ Procedure Test Solution Dissolve given sample in distilled water. Add 2 mL thioglycolic acid . Make alkaline with dilute ammonia. Dilute to 50 mL with distilled water. Standard Solution Prepare a solution of 20 ppm Fe³⁺ . ...