A Calorimetric Investigation of the Copper-Zinc System
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a transportation method to determine the activities in liquid alloys. Baker l3 measured the boiling point of liquid copper-zinc alloys, at various pressures in the temperature range of 1373 to 1473 K. B. Calorimetry Of the many types of calorimeters, "drop" calorimeters have been commonly used in the study of high temperature thermal properties. In this type of calorimetry, the sample is heated to a known temperature and then dropped into the calorimeter heat sink-usually operated around room temperature. '\ Various types of heat sinks have been devised and include fluids such as: water, aniline and paraffin oil, a metal vessel submerged in water, mixtures such as ice, water, and frozen and liquid ether, and a massive block of metal, such as copper or aluminum, surrounded by a constant temperature bath, or by an adiabatic shield. Apart from many experimental difficulties, relatively accurate data can be obtained by proper design of the furnace, dropping mechanism, heat sink, and measuring system. One of the main disadvantages of this type of calorimeter in terms of time and labor, however, is that only the total heat content of the sample from the equilibrium temperature, usually room temperature to a certain elevated temperature, can be obtained in a single run. Therefore, several runs have to be made to measure the heat content over a range of temperatures and to determine the heat of transformation. This disadvantage may be eliminated by several other calorimeters which employ adiabatic heating or cooling methods to obtain specific heats and/or heats of transformation. Oelsen'sl4-l6 method of continuous quantitative thermal analysis was selected, as it permits a complete enthalpy-temperature diagram to be obtained from the results of a single experiment.
APPARATUS The major parts of the apparatus, which stands about 3 m high, are shown in Fig. 1. It is comprised of: a furnace for heating the sample, a heat sink for measuring the heat it releases, a thermocouple to measure its temperature during this time, a mechanism for moving the sample and thermo-
ISSN 0360-2141178/1211-0657$00.75/0 © 1978 AMERICAN SOCIETY FOR METALS AND THE METALLURGICAL SOCIETY OF AIME
VOLUME 98, DECEMBER 1978-657
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STAINLESSI I THERMOCOUPLE:- STEEL TUBE - - - i I LEADS
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SLIDING SEAL
THERMOCOUPLE AND SUSPENSION WIRES
SILICA TUBE SAMPLE IN HEATING POSITION
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LID OPERATING LEVERS --------.~LIDS : WATER COOLED HEAT BARRIER COPPER COIL
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COPPER COILS
SAMPLE IN MEASURING POSITION
Fig . I-The calo r i meter assembl y .
couple rapidly from the furnace to the heat sink, and an adiabatic shield and enclosure that surrounds the whole apparatus , s o that an ine r t atmosphere or vacuum can be maintained. The heat sink is based on the principle des cribed by Yamaguchi. 17 , l B T he heat sink is composed of three fixed and two movable coils. Each is wound with 1.63 mm diam e na me lled copper
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