Beckmann thermometer

A Beckmann thermometer is a device used to measure small differences of temperature, but not absolute temperature values. It was invented by Ernst Otto Beckmann (1853 – 1923), a German chemist, for his measurements of colligative properties. Today its use has largely been superseded by electronic measuring devices.

A Beckmann thermometer's length is usually 40 – 50 cm. The temperature scale typically covers about 5 oC and it is divided into hundredths of a degree. With a magnifier it is possible to estimate temperature changes to 0.001 oC. The peculiarity of Beckmann's thermometer design is a reservoir R at the upper end of the tube (see picture at right), by means of which the quantity of mercury in the bulb can be increased or diminished so that the instrument can be set to measure temperature differences at either high or low temperature values. In contrast, the range of a typical mercury-in-glass thermometer is fixed, being set by the calibration marks etched on the glass or the marks on the printed scale.

Setting the thermometer

In setting the thermometer, a sufficient amount of mercury must be left in the bulb and stem to give readings between the required temperatures. First, the thermometer is inverted and gently tapped so that the mercury in the reservoir lodges in the bend B at the end of the stem. Next, the bulb is heated until the mercury in the stem joins the mercury in the reservoir. The thermometer then is placed in a bath one or two degrees above the upper limit of temperatures to be measured.

If now the upper end of the tube is gently tapped with the finger, or the entire instrument gently tapped on the palm of the hand, the mercury suspended in the upper part of the reservoir will be jarred down, thus separating it from the thread at the bend B. The thermometer will then be set for readings between the required temperatures.

Further details and cautions are given in the following.

External links

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  • Beckmann-Thermometer — absolutes Beckmann Thermometer Das Beckmann Thermometer (nach Ernst Otto Beckmann 1905)[1] ist eine spezielle Bauweise eines Quecksilberthermometers. Es ermöglicht die Messung von Temperaturen mit einer Genauigkeit von 0,01 °C. Erreicht wird dies …   Deutsch Wikipedia

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  • Beckmann thermometer — Bekmano termometras statusas T sritis fizika atitikmenys: angl. Beckmann thermometer vok. Beckmann Thermometer, n rus. термометр Бекмана, m pranc. thermomètre au mercure Beckmann, m; thermomètre Beckmann, m …   Fizikos terminų žodynas

  • Beckmann-Thermometer — Bekmano termometras statusas T sritis fizika atitikmenys: angl. Beckmann thermometer vok. Beckmann Thermometer, n rus. термометр Бекмана, m pranc. thermomètre au mercure Beckmann, m; thermomètre Beckmann, m …   Fizikos terminų žodynas

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  • Beckmann-Thermometer — Bẹck|mann Ther|mo|me|ter [nach dem dt. Chemiker E. O. Beckmann (1853–1923)]: zur ↑ Ebullioskopie u. ↑ Kryoskopie benutztes Quecksilberthermometer, das eine Ablesung auf tausendstel Grad erlaubt. * * * Bẹckmann Thermometer   [nach E. O.… …   Universal-Lexikon

  • beckmann thermometer — noun Usage: usually capitalized B Etymology: after Ernst O. Beckmann : a very sensitive thermometer that has a small range adjustable for any desired values and that is used for determining accurately small differences in temperature (as the… …   Useful english dictionary

  • Beckmann thermometer — /ˌbɛkmən θəˈmɒmətə/ (say .bekmuhn thuh momuhtuh) noun a type of differential thermometer, used for measuring small changes in temperature. Also, Bechmann thermometer …   Australian English dictionary


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