🧪 Limit Test of Arsenic – Principle, Procedure, Reaction, and Viva Questions
🧪 Limit Test of Arsenic – Principle, Procedure, Reaction, and Viva Questions 🔹 Aim: To carry out the Limit Test for Arsenic as per the Indian Pharmacopoeia (IP) standards. 🔹 Principle: The limit test for arsenic is based on the formation of a yellow stain when arsine gas (AsH₃), generated from arsenic in the sample, reacts with mercuric chloride paper . The intensity of the yellow stain produced is compared with a standard to determine if the sample meets the permissible limit. 🔹 Apparatus Required: Arsenic Test Apparatus (Arsenic Test Bottle) Glass Tube with a narrow end Mercuric Chloride Paper Nessler Cylinder (2) for comparison 🔹 Chemicals Required: Arsenic-free zinc granules Lead acetate solution Hydrochloric acid Potassium iodide Stannous chloride Standard arsenic solution Water 🔹 Reaction Involved: Reduction of Arsenic compound: A s 2 O 3 + 6 Z n + 12 H C l → 2 A s H 3 + 6 Z n C l 2 + 3 H 2 O As_2O_3 + 6Zn + 12HCl → ...