Turnover Flange Septa, for Socket

Quick Answer: Turnover Flange Septa for Socket are pierceable rubber stoppers sized to fit the ground-glass joint sockets of flasks and adapters; the plug seals inside the socket and the flange folds down over the outside, closing the vessel so reagents can be added or withdrawn by syringe through the rubber.

Sealing Joints for Air-Sensitive Work

Round-bottom and multi-neck flasks used in synthesis have tapered ground-glass sockets, designed to take condensers, adapters and stoppers. When a neck is not needed for glassware, closing it with a turnover septum turns it into an injection port. Reagents are then added through the rubber by syringe or cannula while the flask stays under a slight positive pressure of nitrogen or argon.

This is standard practice for reactions that are sensitive to air or moisture, such as those using organometallic reagents or dry solvents, and it is equally handy for adding a liquid dropwise without opening a flask. Two-neck and three-neck boiling flasks are typical partners: one neck for a condenser, one for a thermometer or gas inlet, and one sealed with a septum for additions.

Septa for ground-glass sockets are sized to the nominal joint size. The folded flange grips the outside of the joint’s rim, so the septum stays in place when the flask is swirled or warmed in a bath. The image filename describes a serrated, natural-rubber design, in which ridges on the plug improve grip on the ground glass; the exact design supplied should be checked with the order.

Applications

• Closing a spare neck of a multi-neck flask as an injection port.
• Adding air- or moisture-sensitive reagents by syringe under nitrogen or argon.
• Taking small samples from a reaction for TLC monitoring without opening the flask.
• Sealing adapters on Schlenk-type glassware in teaching and research labs.

Specifications

Care & Handling

• Match the septum to the nominal joint size; forcing an oversized septum into a socket can crack thin glass.
• Keep the ground joint clean and dry; the septum grips most securely without grease.
• Vent the flask through a needle or bubbler when heating, so pressure cannot push the septum out.
• Discard septa that are hardened, cracked or heavily punctured.

Why Choose LabEquip

Organic synthesis labs, university research groups and advanced teaching labs are the regular buyers of socket septa. LabEquip lists them with the Turnover Flange Septa, for Test Tube in General Lab Products; joint sizes can be matched through the contact page.

Frequently Asked Questions

What is a septum used for on a flask joint?

It seals the joint while allowing reagents to be added or removed by syringe needle through the rubber, so the flask can stay under inert gas.

How do I choose the right size of socket septum?

Match it to the nominal size of the ground-glass joint, which is usually marked on the glassware. The plug should enter the socket snugly and the flange should fold over the rim without tearing.

Why is the flange folded over the joint?

Folding it over the outside of the rim adds a second grip, so the septum resists being pushed out by slight pressure or dislodged when the flask is moved.

Can I heat a flask sealed with a septum?

Gentle heating is fine if the flask is vented through a needle or connected to an inert-gas line with a bubbler. A sealed flask heated without a vent can build pressure and push the septum out.

Does the ground joint need grease under a septum?

No. Septa are used on clean, dry joints; hydrocarbon greases can make natural rubber swell and loosen its grip.

How can septum life be extended?

Use thin needles, pierce at slightly different points, avoid soaking the rubber in solvent, and store spares away from light and heat.

Last Updated: September 2026