Standard conditions for temperature and pressure

In and, 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 (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 incorporate the reference conditons wherever ambiguity is possible i.e. V(273.15K, 101.325kPa)m3.

In chemistry, standard condition for temperature and pressure (informally abbreviated as STP) are sets of conditions for experimental measurements, to allow comparisons to be made between different sets of data. The most used standards are those of the (IUPAC) and the (NIST), although these are not universally accepted standards. Other organizations have established a variety of alternative definitions for their standard reference conditions. The current version of IUPAC's standard is a of 0 °C (273. 32 °F) and an of 100  (14.504 0.986 atm) while NIST's version is a temperature of 20 °C (293.15 K, 68 °F) and an absolute pressure of 101.325 kPa (14.696 psi, 1 atm). International Standard Metric Conditions for natural gas and similar fluids is 288.15 Kelvin and 101.325 kPa.