LIQUEFACTION. When heat is supplied in sufficient quantity to a solid body, it changes its form and becomes liquid. When this change takes place In tho ease of ice the process is called liquefaction, but in the case of metals fusion. So also if beat be abstracted in suffi cient quantity from a liquid, it usually becomes solid, which process, in the case of bodies which under ordinary circumstances are liquid, such as water, oil, &c., is called congdation ; but for bodies which are usually solid, such as the metals, the process is called solidification.
The more important phenomena attending liquefaction are stated under LATENT HEAT. [See also FnEezmo MixTunrs; HEAT.] Bodies require very various amounts of heat for liquefaction. Mercury, for example, fuses at 39' below zero, wrought iron above +3280°. The following table contains tho fusing points of the substances named :— The fusing points of alloys are often much lower than the fusing point of either of their components. An alloy of two parts bismuth, one of lead, and ono of tin, fuses at 200'. The alloy of eight parts bismuth, five of lead, and three of tin, fuses a little below 212° : the addition of one part mercury renders it still more fusible. It is a very convenient substance for taking casts. When this fusible metal,
as It is called, is poured upon a marble slab, and broken as soon as it Is cool enough to be handled; its surfaces are bright and conchoidal, but the metal is very brittle. Soon, however, it becomes very hot, ceases to be brittle, and the fractured surface becomes granular and dull ; this change of temperature must arise from some now molecular arrangement of the particles after solidification ; it does not appear to be due to the evolution of latent heat, arising from the solidifica tion of the Interior after that of the exterior crust, as has been suggested. The metal after falling to 00' has been known to rise to 150'. The use of fluxes by the metallurgist and others affords numerous illustrations of the fact that mixtures of various bodies fuse at lower temperatures than their component parts do separately. Mixtures of various malts illustrate the same fact :—thus, nitrate of potash fuses at 642', nitrate of soda at 501', hut a mixture of the two salts in equivalent proportions liquefies as low as 429'.
Under the combined Influence of pressure and cold most of the gases hays been liquefied and even solidified as noticed under GASES, LtQui: FACTION OE.