Evaporating Dish, Round Form

Quick Answer: A round form evaporating dish is a shallow laboratory dish with a curved, round bottom and usually a pouring lip, commonly made of glazed porcelain, used to evaporate solutions and crystallise salts over a gauze, a pipeclay triangle or the rings of a water bath.

Why a Round Bottom

The curved base of this dish is shaped for heating from below at one spot: a Bunsen flame under a gauze, or steam rising through the concentric rings of a water bath. The curve spreads the heat, draws the solution towards the centre as it concentrates, and makes the last residue easy to gather and scrape out with a spatula. A round-bottomed dish also nests steadily in a water-bath ring of the right size.

The classic school use is making crystals of copper(II) sulfate: the solution is heated in the dish until a drop taken out on a glass rod forms crystals on cooling, and it is then left to cool and crystallise. The same technique serves for other soluble salts, such as those made by reacting an acid with a metal oxide or carbonate.

On a flat hot plate a round-bottomed dish touches only in the middle, so the flat form evaporating basin suits hot plates better. Material, capacity and diameter are not stated in the listing; evaporating dishes of this shape are most often glazed porcelain.

Practicals That Use It

• Crystallising copper(II) sulfate and other soluble salts.
• Evaporating filtrates in salt-preparation practicals.
• Concentrating solutions on a water bath where overheating must be avoided.
• Recovering salt from rock salt or sea water in introductory chemistry.

Specifications

Care & Handling

• Test for the crystallisation point with a glass rod rather than evaporating to dryness.
• Warm the dish over a small flame before turning the flame up.
• Let the dish cool on a heat-resistant mat, not a wet bench.
• Wash it promptly while residues are still soluble.

Why Choose LabEquip

Every school chemistry lab uses round evaporating dishes for salt preparations, and colleges order them in class sets. LabEquip lists this dish in General Lab Products; let us know the size and number needed through our contact page.

Frequently Asked Questions

How do I know when to stop heating a solution for crystals?

Dip a glass rod into the hot solution and lift it out. If small crystals form on the rod as it cools, the solution is saturated enough; stop heating and let it cool slowly.

Can the dish be heated directly in a flame?

It is normally heated on a gauze over a tripod, or on a triangle for stronger heating. A strong flame on one spot can crack porcelain, so heat gently and evenly.

Why use a water bath instead of a flame?

A water bath keeps the dish below 100 °C, so the solution evaporates without spitting and heat-sensitive salts do not decompose. It is slower but gentler than heating with a flame.

Is a round form dish suitable for a hot plate?

It can be used, but the curved base touches the plate only at the centre, so heating is uneven. A flat form evaporating basin is designed for hot plates.

What does the pouring lip help with?

It lets a hot concentrated solution be poured off crystals, or transferred to another container, in a controlled stream without dribbling down the outside of the dish.

How should the dish be cleaned after crystallising a salt?

Dissolve leftover crystals in warm water, wash with detergent and rinse. Coloured stains from metal salts usually lift with a dilute acid rinse followed by water.

Last Updated: September 2026