Silver Mirror Kit

Quick Answer: This silver mirror test kit is used for Tollens’ test, in which an aldehyde reduces the silver ions in ammoniacal silver nitrate to metallic silver. The silver deposits as a bright mirror on the inside of a clean test tube, distinguishing aldehydes from ketones, which give no mirror.

How the Silver Mirror Forms

Tollens’ reagent is prepared by adding sodium hydroxide to silver nitrate solution, giving a brown precipitate of silver oxide, and then adding just enough ammonia solution to dissolve it. The solution now contains the diamminesilver(I) ion, a mild oxidising agent. Warmed gently with an aldehyde, it oxidises the aldehyde to a carboxylate while the silver ions are reduced to silver metal.

In a scrupulously clean test tube, the silver plates evenly onto the glass as a shiny mirror; in a greasy tube it appears as a grey-black precipitate instead. Ketones lack the hydrogen atom on the carbonyl carbon that makes aldehydes easy to oxidise, so they give no reaction. Reducing sugars such as glucose also give a mirror, which makes the test useful for biochemistry topics too.

The title does not list the kit’s contents. Whatever is supplied, clean glassware matters most: many teachers rinse tubes with sodium hydroxide solution and then distilled water before the test, and use new glass test tubes for the clearest mirror.

Specifications

Care & Handling

• Prepare Tollens’ reagent immediately before use and never store it; on standing it can form explosive silver compounds.
• After the test, rinse leftover reagent away promptly, dissolve the mirror with dilute nitric acid in a fume cupboard and collect silver waste separately.
• Warm the tubes in a hot water bath, never over a flame or directly on a heater.
• Wear gloves and goggles; silver nitrate stains skin, and sodium hydroxide and ammonia are corrosive or irritant.

Applications

• Distinguishing aldehydes from ketones in organic chemistry practicals
• Testing sugars such as glucose as reducing sugars
• Silvering the inside of a test tube to show how chemical silvering of glass works
• Practical assessments on tests for carbonyl compounds

Why Choose LabEquip

Chemistry teachers and college technicians preparing carbonyl tests use a silver mirror kit for its clear, memorable result. LabEquip lists it with other chemistry lab equipment; the contents list can be requested through the contact page.

Frequently Asked Questions

Why must Tollens’ reagent be made fresh?

Ammoniacal silver solutions left standing can form explosive silver compounds. Prepare only the amount needed, use it straight away, and wash away any leftover reagent promptly after the practical.

Why do ketones not give a silver mirror?

Aldehydes have a hydrogen atom on the carbonyl carbon and are easily oxidised to carboxylic acids. Ketones lack that hydrogen and resist oxidation by mild oxidising agents such as Tollens’ reagent.

Why did I get a black precipitate instead of a mirror?

The silver formed but did not stick to the glass evenly. A tube that is not perfectly clean, or heating too fast, gives a grey-black deposit. Clean the tubes with alkali and distilled water and warm them gently in a water bath.

Does glucose give a silver mirror?

Yes. Glucose is a reducing sugar with an aldehyde group in its open-chain form, so it reduces Tollens’ reagent. Fructose also gives a positive result under the test’s alkaline conditions.

How do I remove the silver mirror from the test tube?

Add a little dilute nitric acid in a fume cupboard; it dissolves the silver. Collect the washings as silver waste rather than pouring them away.

How does Tollens’ test compare with Fehling’s test?

Both detect aldehydes. Tollens’ reagent is based on silver and gives a mirror; Fehling’s is based on copper(II) ions and gives a red precipitate. Aromatic aldehydes such as benzaldehyde give a positive Tollens’ test but usually do not react with Fehling’s solution.

Last Updated: September 2026