Gas Washing Bottle

Quick Answer: A gas washing bottle is a glass bottle with a head carrying two tubes: a long inlet that releases gas beneath a liquid and a short outlet above it. Bubbling a gas through the liquid dries it, removes impurities or tests it, as when chlorine is dried with concentrated sulfuric acid.

How Gas Washing Works

Gas enters through the long inlet tube, leaves its tip under the liquid and rises as bubbles. Whatever the liquid absorbs or reacts with stays behind, and the cleaned gas gathers in the head space and leaves by the short outlet tube. Contact improves with smaller bubbles and a slower flow, which is why some designs end the inlet in a sintered glass disc. The same apparatus is often called a Drechsel bottle.

Connecting it the right way round matters more than anything else. If gas is fed into the short tube, pressure builds above the liquid and drives it up the long tube and into the next piece of apparatus, which is dangerous when the liquid is concentrated sulfuric acid. Mark the inlet before assembly, and place an empty bottle as a trap wherever suck-back is possible.

Several bottles are often run in series, for example water first to remove hydrogen chloride from chlorine, then concentrated sulfuric acid to dry it. Upstream, a Woulf bottle can serve as the gas generator, and downstream a gas jar with ground flange collects the washed gas.

Applications

• Drying chlorine, sulfur dioxide, carbon dioxide or oxygen by passing them through concentrated sulfuric acid
• Removing hydrogen chloride from chlorine with water, or from carbon dioxide with sodium hydrogencarbonate solution
• Testing for carbon dioxide by bubbling a gas stream through limewater in respiration or combustion experiments
• Absorbing an acidic exit gas in sodium hydroxide solution so it does not escape into the room
• Serving, empty, as a safety trap that catches liquid drawn back from a later vessel

Specifications

Care & Handling

• Clamp the bottle to a retort stand: filled with sulfuric acid it is heavy, and a tug on the tubing can topple it.
• If the head fits on a ground joint, grease it lightly and secure it so gas pressure cannot lift it.
• Dispose of spent concentrated sulfuric acid by adding it slowly to a large volume of water, never the reverse, and follow your laboratory waste procedure.
• Back-flush a sintered inlet with water after use so salts do not dry in the pores.

Why Choose LabEquip

Gas washing bottles are bought mainly by school and college chemistry departments for gas-preparation practicals, and by laboratories that need to dry or scrub a gas stream. LabEquip lists this item in its Lab Glassware category; state the capacity and inlet type you need via the contact page.

Frequently Asked Questions

Which tube is the inlet on a gas washing bottle?

The inlet is the long tube reaching almost to the bottom, so incoming gas has to bubble up through the liquid. The outlet is the short tube ending in the head space. Connected the wrong way round, gas pressure pushes the washing liquid out through the long tube into the next piece of apparatus.

What liquid should go in the bottle?

It depends on the job: concentrated sulfuric acid to dry gases such as chlorine, oxygen or carbon dioxide; water to absorb hydrogen chloride carried over with chlorine; sodium hydrogencarbonate solution to remove hydrogen chloride from carbon dioxide; and limewater to test for carbon dioxide.

Which gases should not be dried with concentrated sulfuric acid?

Ammonia, because it is a base and reacts with the acid, and hydrogen sulfide, which the acid oxidises. Ammonia is usually dried over quicklime (calcium oxide) in a drying tower instead.

How full should the bottle be?

Add enough liquid to cover the end of the inlet tube by a few centimetres and leave generous head space above it. Overfilling lets bubbles carry liquid into the outlet, while too little liquid lets gas pass through with poor contact.

What is suck-back and how is it prevented?

If gas generation slows or a heated flask cools, the pressure falls and liquid can be drawn backwards into the generator, sometimes violently when concentrated acid meets water. Fit an empty trap bottle between generator and washer, and disconnect the delivery tube before removing the heat.

Does it matter whether the inlet has a sintered disc?

Yes. A sintered (fritted) inlet breaks the gas into fine bubbles and improves contact, but it can clog with precipitate and needs back-flushing, while a plain tube is easier to clean. The product name does not say which this listing has, so mention your preference when you enquire.

Last Updated: September 2026