Pneumatic Trough, Plastic

Quick Answer: A plastic pneumatic trough is a water-filled plastic basin in which gases are gathered by pushing water out of an upturned vessel. A gas jar, test tube or measuring cylinder is filled with water and stood mouth-down in it, and gas entering from a delivery tube rises into the vessel, so the amount collected can be seen.

Why Plastic Suits a Gas-Collection Trough

A pneumatic trough is filled with water, carried to the sink and back, and knocked against glass jars and cylinders throughout a practical. A plastic trough is light when empty, will not shatter if dropped, and is less likely to chip the rims of gas jars stood in it. The listing does not state the plastic, its transparency or its dimensions, nor whether a beehive shelf is included, so confirm those if they matter for your practical.

The collecting method is the same as in any trough. Hydrogen, oxygen and nitrogen, which dissolve very little, are collected efficiently; carbon dioxide dissolves somewhat, so a little is lost. The trough also becomes a simple measuring system: a measuring cylinder full of water, inverted and clamped in the trough, shows the volume of gas produced at intervals, which is how many schools follow the rate of reaction between magnesium and hydrochloric acid.

Compare the pneumatic trough listed without a stated material, and the gas jar with ground flange and foot used to collect and store the gas.

Applications

• Collecting oxygen from hydrogen peroxide with a manganese(IV) oxide catalyst and testing it with a glowing splint
• Measuring the hydrogen given off by magnesium and dilute acid over time, to plot a rate curve
• Collecting hydrogen for the squeaky pop test in lower secondary lessons
• Measuring oxygen released by pondweed in light, in biology practicals on photosynthesis

Specifications

Care & Handling

• Fill the trough only to a depth that covers the mouth of the inverted vessel, leaving room for the water it displaces.
• Keep hot delivery tubes and burners away from the plastic, which can soften or distort with heat.
• Empty and dry the trough after use so algae and limescale do not build up.
• Clean with a soft cloth and mild detergent rather than abrasive powders, which scratch plastic.

Why Choose LabEquip

Schools that run gas-preparation and rate practicals for whole classes often want a plastic pneumatic trough on every bench, because it survives daily handling. LabEquip stocks them in the chemistry lab equipment category; give the number of benches to equip on the contact page.

Frequently Asked Questions

Is a plastic trough as good as a glass one?

For collecting gas over water, yes: the water does the work and the trough only holds it. Plastic is lighter and does not break, which suits student use. Glass is chosen mainly where heat is involved or clear side views are essential.

How can I measure the volume of gas collected?

Fill a measuring cylinder with water, invert it in the trough without letting air in, and clamp it with its mouth under the water. The gas collected pushes the water level down, and the volume is read against the scale.

Can carbon dioxide be collected in the trough?

It can, though some dissolves in the water, so volumes read slightly low. For measuring carbon dioxide accurately a gas syringe is usually better; for simply filling jars, collection over water works well.

Which gases should not be collected over water?

Ammonia, hydrogen chloride and sulfur dioxide are too soluble: they dissolve in the water instead of collecting. Ammonia, being lighter than air, is collected by upward delivery into a dry inverted jar, and the two denser gases by downward delivery.

Why should the water levels inside and outside the cylinder match?

When the levels are equal, the gas inside is at atmospheric pressure, so the volume reading is fair. If the inside level is higher, the gas is at slightly reduced pressure and occupies a larger volume.

How do I keep the trough clean between lessons?

Empty it after each session, rinse out any reaction residues and let it dry upside down. Occasional washing with dilute vinegar removes limescale from hard water without scratching the plastic.

Last Updated: September 2026