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ANALYTICAL EDITION
short condensed heating surface at a higher temperature. The Ioss of heat by radiation to the pipe may be serious, but the effect of radiation on the two thermometers is identical and hence causes no error. 3. The temperature difference produced in the gas must be great enough to be read accurately on the thermometers used, but should be kept as low as is compatible with accuracy t o prevent excessive heat losses to the surroundings. 4, Thermometers be placed at a sufficient distance from the heating element to allow the gas temperature to equalize throughout the stream, but not far enough to allow a substantial mount of heat to escape from the gas to the Pipe. In the experiments of this laboratory the pipe was 5 inches (12.7 cm.) in diameter and the thermometers were placed 25 inches (63.5 cm.) on each side of the heater.
Vol. 4, No. 1
5. A sheet asbestos lining placed in the pipe from thermometer to thermometer increases the accuracy of measurement. It was possible to measure, with a simple adaptation of this method, gas velocities through 5-inch Pipe of 40 to 100 pounds of carbon dioxide pas Der hour (1linear foot Der second and higher) at a pressur
