Two-Neck Adapter, One Vertical, One Angled

Quick Answer: A two neck adapter with one vertical and one angled neck is a glass fitting that enters a single-neck flask through one cone and provides two sockets above it: one straight up and one leaning outwards. The vertical neck takes the main item, the angled neck an accessory such as a thermometer or gas inlet.

Why One Neck Leans

An angled side neck moves the second item away from the first. With a reflux condenser in the vertical neck, the angled neck leaves room for a thermometer adapter, an inlet tube for nitrogen or a stopper through which solid reagents are added, without the clamps and bodies of the two pieces colliding. The angle also points a thermometer or inlet tube towards the centre of the flask below, where the liquid is.

Compared with the parallel two-neck adapter, this pattern suits pairs where only one item must be vertical. It is less suitable where both items are tall and heavy, since glassware in the angled neck leans and needs its own clamp set at the same angle.

The title does not give the angle, the joint sizes or the spacing between the necks. For work where the side neck will take a thermometer, measure how far the thermometer must reach before choosing the flask size.

Applications

Reflux with a thermometer in the angled neck reading the liquid temperature
Reactions under nitrogen, with the gas inlet in the angled neck
Adding solids through the angled neck while a condenser stays in the vertical one
Distillations that need a second opening for an inlet beside the still head

Care & Handling

Set a clamp at the same angle as the side neck if anything heavier than a thermometer adapter goes in it.
Choose a thermometer long enough to reach the liquid through the angled neck without touching the flask wall.
Store the adapter with both sockets protected, since the angled neck projects and is easily knocked.

Specifications

Lower end	Single ground cone for the flask neck
Vertical neck	Socket for a condenser, still head or stirrer guide
Angled neck	Socket for a thermometer, inlet, funnel or stopper
Alternative	Parallel two-neck adapter when both items must stand upright
Angle and joint sizes	Confirm at enquiry

Why Choose LabEquip

Teaching and research labs choose this adapter when a reaction needs a condenser plus one smaller accessory on an ordinary single-neck flask. LabEquip lists it in the chemistry lab equipment range; share your flask and accessory joint sizes on the contact page.

Frequently Asked Questions

What goes in the vertical neck and what in the angled one?

The vertical neck takes the item that must be upright, such as a reflux condenser, still head or stirrer guide. The angled neck takes a thermometer, gas inlet, stopper or powder funnel.

Why is the side neck angled?

The angle moves the second item clear of the first and points it towards the centre of the flask, so a thermometer or inlet tube reaches the liquid.

Can I put a dropping funnel in the angled neck?

A small funnel can be used if it is clamped at the same angle and its stem delivers into the flask rather than onto the wall. For a large funnel, the parallel two-neck adapter is easier.

Is this the same as a Claisen adapter?

Not exactly. A Claisen adapter usually has both necks vertical, one offset by a bend, and is used mainly in vacuum distillation to keep splashes out of the condenser. This pattern has one neck leaning outward.

How do I read the temperature of the liquid through the angled neck?

Use a thermometer adapter in the neck and slide the thermometer down until its bulb is in the liquid but clear of the flask base and any stirrer bar.

How do I support glassware in the angled neck?

Light items such as a thermometer adapter or stopper need no support. Anything heavier should have its own clamp set to the same angle so no side load reaches the joint.

Last Updated: September 2026