When an inverted funnel is placed over a sublimate, the gas collected inside the funnel is typically the vapour of the sublimate itself. Sublimation is the process by which a solid changes directly into a gas without passing through the liquid phase. As the sublimate is heated, its particles gain energy and escape into the air as a gas. These gas particles then condense back into a solid form on the cooler surfaces of the funnel, forming a layer of sublimate on the inside of the funnel.

The gas collected in the inverted funnel can be identified by its chemical properties and physical characteristics. For example, if the sublimate is camphor, the gas collected in the funnel will have a strong, pungent odour and will be highly flammable. If the sublimate is iodine, the gas collected in the funnel will have a violet colour and will react with starch to form a blue-black complex.

The gas collected in the inverted funnel can also be used to determine the vapour pressure of the sublimate. Vapour pressure is the pressure exerted by the vapour of a substance when it is in equilibrium with its liquid or solid phase. By measuring the pressure of the gas collected in the inverted funnel, it is possible to calculate the vapour pressure of the sublimate at a given temperature.