why is the tube packed with dried cotton wool impregnated with lead acetate solution while carrying out limit test for arsenic
Answers
Answer:
Arsenic's limit test is based on the reaction of arsenic gas with hydrogen ion to form yellow stain on reaction with mercuric chloride paper in the presence of reduction agents such as potassium iodide. It is also called a Gutzeit test and requires special equipment. Arsenic, which is present in the sample as arsenic acid, is reduced to arsenic acid by reducing agents such as potassium iodide, stan acid, zinc, hydrochloric acid, etc. Hydrogen further reduces arsenic acid to arsine (gas) and reacts to form yellow stain on reacting with mercuric chloride paper. Cotton wool dipped in a solution of lead acetate is used to trap any hydrogen sulfide gas released with arsine gas.
Explanation:
Lead acetate cotton wool is used in the limit test for arsenic to form stain which is used for the comparison of the results.
Limit test is referred to as qualitative or semi- quantitative test designed to detect and limit small quantities of impurities that are commonly present in pharmaceutical substance.
impurity in a sample with that produced in a standard are then compared.