. The Ontario high school physics. ice-water,because the air in innnediate contact with it is chilled belowthe dew-point. This action is typical of what goes on on alarge scale in the deposition of dew. After sunset, especiallywhen the sky is clear, small bodies at the earths surface, suchas stones, blades of grass, leaves, cobwebs, and the like, coolmore rapidly than the surrounding air. If tlieir temperaturefalls below the temperature of saturation, dew is deposited onthem from the condensation of the vapour in the films of airwhich envelope them. If the dew-point is below the freezing-point
. The Ontario high school physics. ice-water,because the air in innnediate contact with it is chilled belowthe dew-point. This action is typical of what goes on on alarge scale in the deposition of dew. After sunset, especiallywhen the sky is clear, small bodies at the earths surface, suchas stones, blades of grass, leaves, cobwebs, and the like, coolmore rapidly than the surrounding air. If tlieir temperaturefalls below the temperature of saturation, dew is deposited onthem from the condensation of the vapour in the films of airwhich envelope them. If the dew-point is below the freezing-point the moisture is deposited as frost. 300. Rain, Snow and Hail. The cloud globules gravitateslowly towards the earth. If they meet with conditionsfavourable to vaporization they change to vapour again, butif with conditions favourable to condensation they increase insize, unite, and fall as rain. When the condensation in tlie upper air takes place at atemperature below the freezing-point, the moisture crystallizes DISTILLATION 2G5. in snow-flakes. At low temperatures, also, vapour becomestransformed into ice pellets and descends as hail. The hail-stones usually contain a core of closely packed snow crystals,but the exact conditions under which they are formed are notyet fully understood. 301. Distillation. Distillation is a process of vaporizationand condensation, maintained usually for the purpose of freeinga liquid from dissolvedsolids, or for separatingthe constituents of amixture of liquids. Fig-291 shows a simple formof distillation li({uid to be distilledis evaporated in the flaskA, and the product of the condensation of the ^*- 291-I>i«tillation apparatus. vapour is collected in the receiver B. The pipe connecting Aand B is kept cold by cold water made to circulate in thejacket which surrounds it. The separation of liquids by distillation depends on theprinciple that different liquids have different boiling points,and consequently are vaporized and can b
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishe, booksubjectphysics
