{"id":3224,"date":"2023-05-02T06:47:09","date_gmt":"2023-05-02T06:47:09","guid":{"rendered":"https:\/\/thermibel.be\/faq\/what-is-a-fixed-point-how-many-of-them-are-there\/"},"modified":"2023-06-23T14:48:07","modified_gmt":"2023-06-23T14:48:07","slug":"what-is-a-fixed-point-how-many-of-them-are-there","status":"publish","type":"faq","link":"https:\/\/thermibel.be\/en\/faq\/what-is-a-fixed-point-how-many-of-them-are-there\/","title":{"rendered":"What is a fixed point? How many of them are there?"},"content":{"rendered":"\n

The ITS (International Temperature Scale) uses 17 temperature reference points<\/strong> based on the physical phenomenon of the triple point, the vapour pressure, the freezing point, melting point and solidification point of different substances. These distinct points occur at a fixed, reproducible temperature, determined by nature. They do not require the use of a reference sensor in order to measure them. For example, gallium always<\/strong> melts (goes from solid state to liquid state) at 29.7646\u00b0C. A distinct fixed point is the triple point<\/strong>. And a distinct triple point is the triple point of water<\/strong> (0.01\u00b0C under 1 atm). <\/p>\n\n

The triple point<\/strong> is the point at which the vaporisation curve, the sublimation curve and the fusion curve of a substance meet. It was Josiah W. Gibbs (1839-1903) who recognised and proposed the phase rule: the three states, solid, liquid, gas, only coexist at one unique point within the thermodynamic parameters, the triple point. Vapour, liquid and solid are found together at a unique defined temperature and pressure. <\/p>\n

\n
\"Figure<\/figure>\n<\/div>\n

Figure 1. Change in pressure with temperature for the triple point of water<\/p>\n","protected":false},"featured_media":0,"template":"","format":"standard","class_list":["post-3224","faq","type-faq","status-publish","format-standard","hentry"],"acf":[],"aioseo_notices":[],"yoast_head":"\nWhat is a fixed point? How many of them are there? - Thermibel<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/thermibel.be\/en\/faq\/what-is-a-fixed-point-how-many-of-them-are-there\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"What is a fixed point? 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