Table of Contents
What is a Tollens Reagent?
Tollens’ reagent which was initially discovered by a German chemist Bernhard Tollens and so is the name of the reagent, consists of silver ammonia complex in ammonia solution. Sodium hydroxide present in the solution maintains a basic pH i.e. (pH>7) of the solution.
A Tollens reagent is a chemical compound used to test for the presence of aldehydes in a sample. The Tollens reagent is a silver nitrate solution that is mixed with ammonia. When aldehydes are present in a sample, they will react with the Tollens reagent to produce a silver mirror.
What is the Purpose of Tollen’s Test?
The purpose of Tollen’s test is to determine if a person has an allergy to a particular food. The test is performed by placing a small amount of the food allergen in contact with the skin of the forearm and then monitoring the skin for a reaction. If a reaction occurs, it will be visible as a raised, itchy red rash.
Tollens’ Reagent Preparation
Silver nitrate is dissolved in water and then added to a test tube. Ammonia gas is then bubbled through the solution. A silver mirror will form on the inside of the test tube.
Tollens’ Test
The Tollens’ test is a test for aldehydes and ketones. A small amount of silver nitrate is added to a test tube of the substance being tested. A positive result will cause a silver mirror to form on the inside of the test tube.
Example of Tollens’ Test
- A silver mirror is placed in a solution of AgNO 3 . A precipitate of silver chloride forms on the mirror. The mirror is then removed from the solution and dried.
- A Tollens’ test is then performed on the mirror. A positive test results in the formation of a silver mirror.
- The silver mirror formed in the Tollens’ test confirms the presence of silver chloride in the solution.
