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Since 1982, STP has been defined as a temperature of 273.15 K (0 °C, 32 °F) and an absolute pressure of exactly 10 5 Pa (100 kPa, 1 bar). NIST uses a temperature of 20 °C (293.15 K, 68 °F) and an absolute pressure of 1 atm (14.696 psi, 101.325 kPa). [3] This standard is also called normal temperature and pressure (abbreviated as NTP).
The system can be traced back to the measuring systems of the Hindus [18]: B-9 and the ancient Egyptians, who subdivided the hekat (about 4.8 litres) into parts of 1 ⁄ 2, 1 ⁄ 4, 1 ⁄ 8, 1 ⁄ 16, 1 ⁄ 32, and 1 ⁄ 64 (1 ro, or mouthful, or about 14.5 ml), [19] and the hin similarly down to 1 ⁄ 32 (1 ro) using hieratic notation, [20] as ...
Standard cubic centimeters per minute (SCCM) is a unit used to quantify the flow rate of a fluid. 1 SCCM is identical to 1 cm³ STP /min. Another expression of it would be Nml/min. These standard conditions vary according to different regulatory bodies.
The standard liter per minute (SLM or SLPM) is a unit of (molar or) mass flow rate of a gas at standard conditions for temperature and pressure (STP), which is most commonly practiced in the United States, whereas European practice revolves around the normal litre per minute (NLPM). [1] Until 1982, STP was defined as a temperature of 273.15 K ...
And finally, the centimetre and square centimetre are used in the normal way to measure thickness and area. The cm corresponds in the permeability equations to the thickness of the material whose permeability is being evaluated, the cm 3 STP cm −2 s −1 to the flux of gas through the material, and the cmHg to the pressure drop across the ...
The standard state of a material (pure substance, mixture or solution) is a reference point used to calculate its properties under different conditions.A degree sign (°) or a superscript Plimsoll symbol (⦵) is used to designate a thermodynamic quantity in the standard state, such as change in enthalpy (ΔH°), change in entropy (ΔS°), or change in Gibbs free energy (ΔG°).
Approximate measures. Approximate measures are units of volumetric measurement which are not defined by a government or government-sanctioned organization, or which were previously defined and are now repealed, yet which remain in use. [1][2][3] It may be that all English-unit derived capacity measurements are derived from one original ...
Conversions between units in the metric system are defined by their prefixes (for example, 1 kilogram = 1000 grams, 1 milligram = 0.001 grams) and are thus not listed in this article. Exceptions are made if the unit is commonly known by another name (for example, 1 micron = 10 −6 metre).