EXPANSION

From Agepedia

EXPANSION, in physics, is the enlargement or increase in the bulk of bodies, in consequence of a change in their temperature. (See Caloric.) This is one of the most general effects of heat, being com mon to all bodies whatever, whether solid or fluid. The expansion of solid bodies is determined by the pyrometer, and that of fluids by the thermometer (see these articles). The expansion of fluids varies considerably; but, in general, the denser the fluid, the less the expansion; thus water expands more than mercury, and spirits of wine more than water ; and, commonly, the greater the heat, the greater the expansion; but this is not universal, for there are cases in which expansion is produced, not by an increase, but by a diminution of temperature. Water furnishes us with the most remarkable instance of this kind. Its maximum of density corresponds with 42°.5 of Fahrenheit's thermometer; when cooled down below 42°.5, it undergoes an expansion for every degree of temperature which it loses; and at 32°, the expansion amounts t0 Tfftf °f me wn°le expansion which water undergoes when heated from 42°.5 to 212°. With this more recent experiments coincide very nearly ; for, by cooling 100,000 parts in bulk of water from 42°.5 to 32°, they were converted to 100,031 parts. The expansion of water is the same for any number of degrees above or below the maximum of density. Thus, if we heat water 10° above 42°.5, it occupies precisely the same bulk as it does when cooled down to 10 degrees below 42°.5. Therefore the density of water at 32° and at 53° is precisely the same. Dalton cooled water to the temperature of 5° without freezing, or 37°.5 below the maximum point of density; and, during the whole of that range, its bulk precisely corresponded with the bulk of water the same number of degrees above 42°.5. The prodigious force with which water expands in the act of freezing, is shown by glass bottles filled with water, which are commonly broken in pieces when the water freezes. A brass globe, whose cavity is an inch in diameter, may be burst by filling it with water and freezing it; and the force necessary for this effect is 27,720 pounds weight. The expansive force of freezing water may be explained by supposing it the consequence of a tendency which water, in consolidating, is observed to have to arrange its particles in one determinate manner, so as to form prismatic crvstals, crossing each other at angles of 60° and 120°. The force with which they arrange themselves in this manner must be enormous, since it enables small quantities of water to overcome so great mechanical pressures. This observation is conspicuously illustrated by observing the crystals of ice on a piece of water exposed to the action of the air in frosty weather; or upon a pane of glass in a window of a room without a fire, at the same season. Various methods have been tried to ascertain the specific gravity of ice at 32°; that which succeeded best was to dilute spirits of wine with water till a mass of solid ice put into it remained in any part of the liquid without either sinking or rising. The specific gravity of such a liquid is 0.92, which, of course, is the specific gravity of ice, supposing the specific gravity of water at 60° to be 1. This is an expansion much greater than water experiences even when heated to 212°, its boiling point. We see from this that water, when converted into ice, no longer observes that equable expansion measured by Dalton, but undergoes a very rapid and considerable augmentation of bulk.Ex PARTE ; a term used in the court of chancery, when a commission is taken out and executed by one side or party only, upon the other party's neglecting or refusing to join therein.