An Efficient and Inexpensive Device for Measurement of Gas Volume
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Gas volume is typically measured with the use of a gas meter or a gas flowmeter. Agas meter allows the 'ah admittance of a controlled volume of gas. A gas flowmeter measures the gas flow rate: the volume of gas n -Gr can be calculated by multiplying the gas flow rate by the time of flow. In our laboratory, we have been stc$9ef using a simple and inexpensive device far measurement of gas volume with very satisfactory results. A8 shown in the figure, the device consists of two 14L 15-L drinking water bottles (Battle A and Battle B), each tightly closed with a two-hole rubber stopper. Two short right-angle tubes are inserted into the two rubber stappers as indicated.. The short tube in Bottle A is for connection to the source of gas to be measured; t h e other short tuhe i n Bottle B is for connection to the vacuum line. The two bottles are connected with vacuum tubing and two long rightangle tubes a s shown in figure. Bottle A is calibrated in liters and is filled to mark with water before use. -8 -A In operation, the vacuum is turned on, the gas to be I S L ~ ~ measured is drawn into Bottle A, and the water disHWOI B O ~ B placed by the gas enters Bottle B through the connecting tuhing. The volume of gas collected is the volume of water displaced in Bottle A. To determine the volume of gas at atmospheric pressure, dose the valve on Bottle Aat the end of gas collection,disconnect the vacuum source, and open Bottle B to the atmasphere. Adjust the vertical positions of the two bottles so that the levels of water in the two battles are a b u t the same. At the same time, water is allowed to flow between the two bottles. When water stops flowing and the two water levels are exactly the same, the pressure of gas inside Battle A is at atmospheric pressure. Remrd the volume of water displaced, which is also the volume of gas at atmospheric pressure.
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Van T. Lieu CaliforniaState University , Long Beach, CA 90840
420
Journal of Chemical Education
