Text-book of medical and pharmaceutical chemistry . ood spirit, etc. Distillation is carried on in aretort or still, and the vapor is condensed in a worm or retort, or still, is the vessel in which the liquid is heated, andis made of glass, copper, iron, or platinum. (See Figs. 8 and 57.) 28 MEDICAL CHEMISTRY. The heat is applied to the retort or still until the liquid vapor from the boiling liquid passes through the beak of theretort into the condenser, which is always kept cool by means ofcold water. A few solid bodies when heated do not melt and form liquids,but pass
Text-book of medical and pharmaceutical chemistry . ood spirit, etc. Distillation is carried on in aretort or still, and the vapor is condensed in a worm or retort, or still, is the vessel in which the liquid is heated, andis made of glass, copper, iron, or platinum. (See Figs. 8 and 57.) 28 MEDICAL CHEMISTRY. The heat is applied to the retort or still until the liquid vapor from the boiling liquid passes through the beak of theretort into the condenser, which is always kept cool by means ofcold water. A few solid bodies when heated do not melt and form liquids,but pass directly into the state of vapor. Such bodies are saidto sublime, and the process is called sublimation. Iodine, sulphur, camphor, and ammonium chloride, are ex-amples of bodies which may be sublimed, and this process isusually employed for their purification. 29. Latent Heat.—It is evident that a part of the heat forceapplied to a body is used up in overcoming the force of cohe-sion and in expanding the body, and does not appear in the Fig. actual moving power of the molecules. In our ball-and-stringillustration (Art. 22), a part of the force applied to the string bythe hand is expended in stretching the string, or finally in break-ing it, and does not appear in the moving power of the force, which is expended in overcoming cohesion, and inkeeping the molecules apart, does not appear in the temperatureof a booy. When air is heated and allowed to expand, abouttwo-sevenths of the heat force is used up in expanding it. If weapply heat to a vessel containing ice, the temperature of thewater formed is the same as that of the ice, although a consider-able heat has been absorbed in the melting process. Wlien water is boiled in an open vessel it does not rise above100° C. (212° F.), however hot the fire; it remains at 100° C. HEAT. 29 until it is all evaporated. What has become of all the heatapplied to the water ? It has been used to drive the moleculesfarther apa
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