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An instrument used to illustrate the freezing of water by its own evaporation. The ordinary form consists of two glass bulbs, connected by a tube of the same material, and containing only a quantity of water and its vapor, devoid of air. The water is in one of the bulbs, and freezes when the other is cooled below 32¡ Fahr.

kr[=i]-of'o-rus, n. an instrument for showing the decrease of temperature in water by evaporation. [Gr. kryos, frost, and pherein, to bear.]

[Gr.] An instrument for showing the cold produced by evaporation. It consists of a glass tube with a short bend at each end, to which are fastened glass bulbs (A and B) which the tube serves to connect. The bulbs can therefore be placed inside two basins or tumblers on a table. One bulb (B) is partly filled with water, and, as the air has been withdrawn and the instrument hermetically sealed, the other bulb (A) and the tube are filled with vapour of water. If the tumbler in which the bulb A is placed be filled with ice, the vapour in A is condensed, and the vacuum thus formed is filled with vapour from the water in B; but this in turn is condensed, and thus a rapid evaporation of the water in B is set up. In this process so much of the heat of the water in B is rendered latent that its temperature rapidly falls, and at last it is converted into ice.