Wedgwood degrees - a unit of temperature in a temperature scale that was used to measure temperatures above the boiling point of mercury - 356 ° C (673 ° F). The scale and related measurement method was proposed by the famous English ceramist and designer Josaya Wedgwood in the 18th century. Measuring the temperature on the Wadgewood scale is based on measuring the amount of shrinkage of clay during heating, by comparing the length of heated and cold clay cylinders. The zero on the Wadgewood scale corresponds to 580.8 ° C (1077.5 ° F), from which the scale was graduated by 240 degrees to the mark of 54 ° C (130 ° F). The measurement principle and numerical characteristics of the Wadgewood scale were subsequently found to be inaccurate and obsolete.
Content
Method History
Using a conventional mercury thermometer, one can measure the temperature only up to the boiling point of mercury - 356 ° C, which is unacceptable for many technological processes, in particular, in the production of ceramics , glass-making and metallurgy . British ceramist and entrepreneur Josiah Wedgwood, in this regard, developed his method and scale for measuring the temperature in furnaces [1] . Initially, the method and devices of Wadgewood became widespread, but after the invention of accurate pyrometers , such as the pyrometer of John Daniel in 1830, fell out of use [2] .
In 1782, Wadgewood built a temperature measuring device (pyrometer), which consisted of two clay cylinders with metal plates inclined at a slight angle, with a scale divided into 240 parts. The cylinder without heating corresponded to zero temperature. After annealing the clay, the second cylinder was compressed and the temperature could be determined according to the degree of its compression [3] [4] .
Scale
The zero mark on the Wadgewood scale corresponded to a red hot temperature of 580.8 ° C (1077.5 ° F). From zero, the scale was graduated down by 240 graduations to a level of 54 ° C (130 ° F) and up to a level of 17 914 ° C (32,277 ° F) [5] . The Weatherwood method was imperfect and drew criticism from many of his contemporaries. In particular, according to academician Ya. D. Zakharov (1765–1836), “by means of this not a single degree of heat, especially in different and distant places, it is impossible to determine precisely”. To the disadvantages of the Wedgwood pyrometer, Ya. D. Zakharov attributed the following:
- different compressibility of different grades of clay with increasing temperature;
- low sensitivity;
- the possibility of deformation and destruction of the cube at the moment of experience;
- inaccurate definition of zero points and more [6] .
Wedgwood also tried to compare his scale with other temperature scales by measuring the expansion of silver depending on temperature, and also determined the melting point of copper (27 ° W or 2531 ° C (4587 ° F)), silver (28 ° W or 2603 ° C (4717 ° F)) and gold (32 ° W or 2892 ° C (5237 ° F)). As it turned out later, all these values, determined by Waggwood, are erroneous (the real melting point of copper is 1084 ° C, silver is 962 ° C, gold is 1064 ° C) [7] .
Adjustment
The French chemist Louis Guiton de Morvo (1737–1816), using his pyrometer, tested the Wadgewood scale and came to the conclusion that its zero mark should be significantly lower — about 269 ° C, not 580.8 ° C; and the lowest point is at 16.9 ° C, not 54 ° C. Nevertheless, even after this, Wadgewood did not abandon his ideas about the melting points of metals [4] .
Notes
- ↑ Chaldecott, JA Presidential Address: Josiah Wedgwood (1730–95): Scientist (Eng.) // The British Journal for the History of Science : journal. - 1975. - Vol. 8 , no. 1 . - P. 1-16 . - DOI : 10.1017 / s0007087400013674 .
- ↑ Elements of chemistry: containing experimental and theoretical .... - 1840. - P. 39.
- ↑ Handwörterbuch der Reinen und Angewandten Chemie ... : [] . - 1854. - P. 713–714.
- ↑ 1 2 Natural Philosophy. Volume 2. Popular Introductions to Natural Philosophy. Newton's Optics. Description of Optical Instruments. Thermometer and Pyrometer. With an Explanation of Scientific Terms, and an Index . - 1832. - P. 27-30. - ISBN 978-0-543-88106-9 .
- ↑ Johann Samuel Traugott Gehler's physikalisches Wörterbuch: Bd., 1. Abth. (1833) N-Pn; 2. Abth. (1834) Po-R . - 1834. - P. 986.
- ↑ Zakharov, 1804 , p. 82
- World The world in a crucible: laboratory practice and geological theory at the beginning of geology . - 2009-02-15. - ISBN 978-0-8137-2449-2 .
Literature
- Ya. D. Zakharov. On the Flamermaker, or Tool, by which it is possible to determine all the degrees of heat // Technological Journal . - 1804. - p . 81 .