Breathing limewater Speakers

Quick Answer: The Breathing limewater Speakers is a limewater breathing apparatus: a set-up in which air breathed in and air breathed out are bubbled through limewater, so students can see that exhaled air turns limewater milky faster because it contains more carbon dioxide. The word “Speakers” in the title is not explained in the listing.

The Inhaled and Exhaled Air Experiment

The classic form of this practical uses two tubes or flasks of clear limewater, a solution of calcium hydroxide, joined to a single mouthpiece by delivery tubes. The tubes are arranged so that when the student breathes in, room air is drawn through the limewater in one vessel, and when the student breathes out, exhaled air is blown through the limewater in the other. The limewater receiving exhaled air turns milky within a few breaths, while the other vessel stays clear far longer.

The milkiness is a precipitate of calcium carbonate, formed when carbon dioxide reacts with calcium hydroxide. The result shows that exhaled air contains more carbon dioxide than inhaled air, evidence that body cells produce carbon dioxide during aerobic respiration and that it is removed in the lungs. If breathing out continues for a long time, the milkiness can clear again as excess carbon dioxide forms soluble calcium hydrogencarbonate, a point worth mentioning to students who over-blow.

The listing gives no description of this item’s parts, and older listing text described it only as a respiration chamber set-up for detecting carbon dioxide with limewater, so confirm the vessels, tubing and mouthpieces supplied, and what “Speakers” refers to, before ordering. Lessons on the mechanics of breathing pair well with the human respiratory system jar model.

Practical Uses

• Comparing carbon dioxide in inhaled and exhaled air in secondary biology
• Showing that respiration in body cells releases carbon dioxide
• Comparing exhaled air at rest and after exercise
• Introducing the limewater test for carbon dioxide in chemistry

Specifications

Care, Hygiene & Safety

• Give each student a clean mouthpiece, and rinse and disinfect the limewater breathing apparatus between users.
• Students should breathe gently and never suck hard, so limewater cannot be drawn into the mouth; limewater irritates the eyes and skin, so wear eye protection and rinse any splashes with water.
• Rinse vessels and tubing with water after use; a white calcium carbonate film can be removed with dilute acid and then rinsed off.
• Replace old or cloudy limewater, which absorbs carbon dioxide from the air when left open.

Why Choose LabEquip

School biology departments buy a breathing limewater set because it gives a clear, quick result that every student can see for themselves. LabEquip lists it among its biology lab products; to confirm what the set includes, send a question through the contact page.

Frequently Asked Questions

Why does limewater turn milky with exhaled air?

Carbon dioxide reacts with the calcium hydroxide in limewater to form calcium carbonate, which is insoluble and appears as a white, milky precipitate. Exhaled air has much more carbon dioxide than inhaled air, so the change happens quickly.

Does inhaled air contain any carbon dioxide?

Yes, but only a small amount. That is why the limewater in the inhaled-air vessel may eventually go slightly cloudy too, but far more slowly than the limewater receiving exhaled air.

Why can the milkiness disappear if a student keeps blowing?

Excess carbon dioxide reacts further with the calcium carbonate and water to form calcium hydrogencarbonate, which is soluble. The liquid then turns clear again, so students should stop once it goes milky.

How is limewater made?

Calcium hydroxide is shaken with distilled water and left to settle, and the clear liquid is filtered or poured off. It should be kept in a stoppered bottle so it does not react with carbon dioxide in the air.

Is the experiment safe for students?

Yes, with care. Each student uses a clean mouthpiece, breathes gently without sucking back, and wears eye protection because limewater is an irritant. The apparatus is cleaned between users.

What does the experiment show about respiration?

It shows that the body gives out carbon dioxide. Cells produce carbon dioxide in aerobic respiration, the blood carries it to the lungs and it leaves in exhaled air.

Last Updated: September 2026