Gas Jar With Ground Flange And Foot

Gas Jar With Ground Flange and Foot

Precision-Ground Flange Interface: The top rim is meticulously ground to a flat, matte finish, enabling a hermetic seal with glass cover plates to prevent gas leakage or atmospheric contamination during sensitive chemical reactions.

High-Stability Integrated Foot: Engineered with a broad, fire-polished base that provides a low center of gravity, ensuring maximum structural stability on laboratory benches even when the vessel is filled with high-density gases.

$4.29

Quick Answer: A gas jar with ground flange and foot is a tall, open-topped glass cylinder whose rim is ground flat so that a greased cover plate can seal it, standing on a wider foot. Chemistry classes use it to collect, hold and test gases.

What the Ground Flange and Foot Do

The ground flange is the working surface of this gas jar. Grinding leaves the rim flat and slightly matt, so a glass cover plate with a thin film of petroleum jelly sits on it without gaps. The collected gas then stays in the jar while it is carried from the collecting trough to the bench, which matters when a jar of oxygen or carbon dioxide has to wait a few minutes for its test. A plain fire-polished rim cannot be closed as reliably.

The foot is a base wider than the body, and it lowers the chance of a tall jar tipping when a burning splint or deflagrating spoon is lowered inside. Two flanged jars can also be placed mouth to mouth with a cover plate between them and the plate then withdrawn, which is how teachers set up the classic diffusion demonstrations.

Applications

Collecting oxygen, hydrogen or carbon dioxide over water in a pneumatic trough, or by displacement of air for gases that dissolve in water
Gas tests: a glowing splint relighting in oxygen, a lighted splint going out in carbon dioxide, or limewater shaken in a covered jar
Burning sulfur, charcoal or magnesium in oxygen on a deflagrating spoon, then testing the product with moist indicator paper
Diffusion demonstrations with two jars placed flange to flange

Specifications

Item	Gas jar: open-topped cylindrical glass jar
Rim	Ground, flat flange for sealing with a cover plate
Base	Foot wider than the body for stable standing
Material	Clear glass (glass type not stated in the listing)
Closure used	Flat glass cover plate with a light film of petroleum jelly
Capacity and height	Confirm at enquiry

Care & Handling

Grease only the ground flange of the gas jar, thinly, and wipe the grease off with tissue before washing so it does not spread through the sink.
Do not scour the ground rim with abrasive powder; scratches across the flange spoil the seal.
Store jars upright on their feet rather than packed inside one another, and check the flange for chips before use, since a chipped rim neither seals nor handles safely.

Why Choose LabEquip

Chemistry teachers usually buy gas jars in class sets for gas-preparation practicals. LabEquip lists this jar in its Lab Glassware range next to apparatus used earlier in the same set-up, such as the Woulf bottle used as a gas generator. Send the quantities and any capacity preference through the LabEquip contact page.

Frequently Asked Questions

Why does a gas jar need a ground flange?

Grinding makes the rim flat, so a greased glass cover plate forms a close seal. Without it, the collected gas escapes or mixes with air before it is tested, giving weak results such as a glowing splint that fails to relight.

What should I use to seal the cover plate?

A thin smear of petroleum jelly on the flange is the usual method. Slide the plate sideways to open or close the jar rather than lifting it, so little air enters. Too much grease contaminates the sample and makes cleaning harder.

Can the gas jar be heated?

No. It is designed for collecting and holding gases at room temperature, not for direct heating. When burning sulfur, charcoal or magnesium inside it, add a layer of sand or water first so hot fragments do not crack the base.

How do I collect a gas that dissolves in water?

Use displacement of air. Ammonia is lighter than air, so collect it in an inverted jar with the delivery tube reaching up to the top. Hydrogen chloride is denser than air, so collect it in an upright jar with the tube reaching the bottom.

How is a gas jar used in a diffusion demonstration?

Two covered jars are stacked flange to flange, one holding a coloured vapour such as bromine and one holding air, and the plates between them are removed. Students watch the colour spread into the upper jar over several minutes. Bromine work belongs in a fume cupboard.

How should gas jars be cleaned after combustion experiments?

Wipe the grease off the flange, then soak in warm water with laboratory detergent and use a soft bottle brush. A dilute acid rinse removes white magnesium oxide deposits. Rinse with water and leave to dry standing upright.

Last Updated: September 2026