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Standard conditions for temperature and pressure are standard sets of conditions for experimental measurements to be established to allow comparisons to be made between different sets of data. The most used standards are those of the International Union of Pure and Applied Chemistry (IUPAC) and the National Institute of Standards and Technology (NIST), although these are not universally accepted standards. Other organizations have established a variety of alternative definitions for their standard reference conditions. In chemistry, IUPAC has established two standards: * standard temperature and pressure (STP) as a temperature of 273.15 K (0 °C, 32 °F) and an absolute pressure of exactly 100 000 Pa (1 bar, 14.5 psi, 0.98692 atm). * standard ambient temperature and pressure (SATP) as a temperature of 298.15 K (25 °C, 77 °F) and an absolute pressure of exactly 100 000 Pa. The STP and the SATP should not be confused with the standard state commonly used in thermodynamic evaluations of the Gibbs energy of a reaction. NIST uses a temperature of 20 °C (293.15 K, 68 °F) and an absolute pressure of 101.325 kPa (14.696 psi, 1 atm). This standard is also called normal temperature and pressure (abbreviated as NTP). The International Standard Metric Conditions for natural gas and similar fluids are and 101.325 kPa.〔 In industry and commerce, standard conditions for temperature and pressure are often necessary to define the standard reference conditions to express the volumes of gases and liquids and related quantities such as the rate of volumetric flow (the volumes of gases vary significantly with temperature and pressure). However, many technical publications (books, journals, advertisements for equipment and machinery) simply state "standard conditions" without specifying them, often leading to confusion and errors. Good practice is to always incorporate the reference conditions of temperature and pressure. ==Definitions== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Standard conditions for temperature and pressure」の詳細全文を読む スポンサード リンク
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