Clear Glass Thistle Funnel For School Labs

Thistle Funnel, Clear Glass

Fire-Polished Stem Terminus: Features a precision-annealed, fire-polished tip that ensures smooth liquid discharge and resists chipping during insertion through rubber stoppers or tight-fitting laboratory bungs.

Standardized Reservoir Geometry: Engineered with a uniform wall distribution throughout the thistle-head, providing enhanced mechanical strength to withstand the lateral pressure of routine manual laboratory handling.

$2.91

Quick Answer: A clear glass thistle funnel is a long glass tube topped by a bulb-shaped cup, used to pour liquid into a closed flask and in the classic thistle funnel osmosis demonstration. The clear glass version suits room-temperature work in school laboratories.

Two Classic School Experiments

The first is gas preparation. To make carbon dioxide, dilute hydrochloric acid is run onto lumps of marble in a flask closed by a two-hole bung; hydrogen is made the same way from zinc granules and dilute sulfuric acid. The funnel passes through one hole with its lower end dipping into the acid, and a delivery tube leaves through the other. Acid is topped up through the cup as the reaction slows, and the submerged tube end stops gas escaping upwards.

The second is osmosis. A piece of partially permeable membrane, such as cellophane, dialysis tubing or the inner membrane of an egg, is tied tightly over the mouth of the cup. The funnel is inverted, filled with concentrated sugar solution up into the stem, and clamped with the membrane immersed in a beaker of water. Over the lesson, water moves into the sugar solution and the level climbs up the tube, which is marked with a pen or a strip of tape to track the rise.

Clear glass, named in the title, is transparent so the moving liquid is easy to watch, but its composition is not stated. Where the generating flask will be heated, the borosilicate thistle funnel is the better match. Tube length and cup size are not fixed in the listing.

Applications

Carbon dioxide or hydrogen generation in school practicals, with acid added through the cup
Thistle funnel osmosis experiments in biology lessons, using sugar solution and a membrane
Showing students how a liquid seal keeps a gas inside an apparatus
Topping up liquid in a closed bottle without removing the bung

Specifications

Material	Clear glass, as named in the title; composition not stated
Form	Bulb-shaped cup on a long tube
Typical uses	Liquid addition in gas generators; thistle funnel osmometer
Heating	Room-temperature work; choose borosilicate for heated set-ups
Tube length and cup diameter	Confirm at enquiry

Care & Handling

Tie the membrane tightly with thread or a rubber band and check for leaks before starting an osmosis run.
Lubricate the tube and bung hole with water before inserting, and protect the hand with a folded cloth.
Do not heat clear glass funnels directly or pour boiling liquid into them.
Wash out sugar solution promptly with warm water, since dried syrup blocks the narrow tube.

Why Choose LabEquip

School science departments buy clear thistle funnels in class quantities for gas preparation and for biology osmosis practicals. LabEquip supplies them from the chemistry lab equipment catalogue; send numbers for your class sets through the contact page.

Frequently Asked Questions

How does the thistle funnel osmosis experiment work?

The sugar solution inside the funnel is separated from pure water by a partially permeable membrane. Water molecules pass through the membrane into the more concentrated solution faster than they leave it, so the volume inside increases and the liquid rises up the tube.

What membrane can I use?

Cellophane, dialysis (Visking) tubing, or the thin membrane from inside an egg shell all work. It must be tied tightly and without wrinkles over the mouth of the cup, otherwise the solution leaks out and no rise is seen.

Why is the clear glass version used in schools?

Most school gas preparations run at room temperature, and osmosis runs need no heat at all, so heat resistance is rarely needed. Clear glass makes the liquid levels easy to see. Heated set-ups call for the borosilicate version.

Why is gas escaping through the thistle funnel?

The end of the tube is probably above the acid. Push the tube down until it nearly touches the bottom of the flask, or add more acid, so the end stays covered throughout the reaction.

How fast should the liquid rise in an osmosis demonstration?

It depends on the membrane area, the sugar concentration and the temperature. With a concentrated sucrose solution a rise is usually visible within the lesson, and marking the level at intervals lets students plot it against time.

Can I use the thistle funnel with concentrated acids?

Glass itself resists most acids, but preparations using concentrated acids often need heating and careful handling. For those, use a heat-resistant borosilicate funnel in a fume cupboard, and keep clear glass funnels for dilute, room-temperature work.

Last Updated: September 2026