Cenco Gas Volume Reduction Circular Slide Rule

This yellow paper circular rule consists of two discs, one with a protruding tab for rotating the disc, held together with a metal grommet. The device reduces the observed volume of a gas to the corresponding volume under standard conditions (0°C, 760 mm pressure). Scales for temperatures from 10 degrees to 35 degrees centigrade and for pressures from 700 to 790 mm run along the lower edge of the rule. Setting the device for an observed temperature and pressure reveals a volume factor and the logarithm of the volume factor in the lower interior of the instrument. The factor is multiplied by the observed volume on the scale along the upper edge of the instrument to arrive at the reduced volume.

The instrument is marked: CentralScientificCo. (/) CENCO (/) CHICAGO U.S.A. (/) GAS VOLUME REDUCTION CHART. It is also marked: Copyrighted 1921, by Central Scientific Co. An advertisement for the "new rotary CENCO hyvac pump," available from Central Scientific's Bulletin No. 92, appears on the back of the device. For another instrument made by Central Scientific Co., see 1982.0147.02.

The front of the instrument indicates that Prof. E. M. Jones of Adrian College in Adrian, Mich., proposed its design. Jones also wrote "Laboratory Versus Recitation," School Science and Mathematics 8 (1923): 749–759. In 1920, he was appointed to the city of Adrian's first water board.

Reference: "Adrian H₂O: Over One Hundred Years," http://www.ci.adrian.mi.us/Services/Utilities/History.aspx.

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