Pressure one atmosphere

Absolute pressure is the sum of atmospheric and gauge pressures. Pressure is also expressed in terms of the height of a column of mercury that would exert the same pressure. One atmosphere is equal to 760 mm (29.9 in) of mercury. 

The Standard state of a substance is its state under standard pressure (one atmosphere) and 298 K. 

Similarly, the term activity, a is defined as the ratio of its fugacity, / to its fugacity at standard state,/°. Standard state is generally taken to be pure substance at standard temperature (298 °K) and pressure (one atmosphere pressure). 

Suppose given the temperature, 25°, and the pressure, one atmosphere. If one wishes the solution to remain in equilibrium in contact with common salt and a couple of precipitates (C, ), there may be given arbitrarily the values of two of the five concentrations Sj, Sj, Sg, 5g, and the values of the other three will follow. We see then that at a given pressure and temperature each couple of precipitates (C, Y)y of which the first does not contain lime and the second is a calcium salt, will correspond to a certain domain S in the system of coordinates Sg, sy, to another domain I in the system Sj, finally, to a third domain in the system... 

Standard temperature and pressure (STP) Standard temperature 0°C (273.15 K), and standard pressure, one atmosphere, are standard conditions for gases. 

The thermodynamic standard state of a substance is its most stable pure form under standard pressure (one atmosphere) and at some specific temperature (25°C or 298 K unless otherwise specified). Examples of elements in their standard states at 25°C are hydrogen, gaseous diatomic molecules, H2(g) mercury, a silver-colored liquid metal,... 

The experimental apparatus and approach have been previously described (18,19) and are summarized briefly here. The sampling mode is an extractive method in which a sampling probe is immersed in the system to be studied. A small orifice at the apex of the cone extracts gas and with a downstream pressure (stage one pressure = 10 torr) that is significantly lower than the source pressure, (one atmosphere in this case) fully developed sonic flow is established. Such an expansion leads to extensive cooling and a more or less abrupt transition to collisionless flow. A second conical... 

In the present eonfiguration, air inlet boundaries are assumed to be Pressure Inlet while outflow boundaries are assumed Pressure Outlet . Pressure inlet boundary conditions were used to define the total pressure and other scalar quantities at flow inlets. Pressure outlet boundary conditions were used to define the static pressure at flow outlets. At the nozzle inlet, the air pressure was varied. At the nozzle outlet, the pressure was supposed to be the external pressure (one atmosphere). At the wall of the nozzle standard wall function boundary condition was applied. Although the high velocity of air stream was a heat source that will increase the temperature in the nozzle, the nozzle length was very short and the process oecurs in a very short time. For simplification, it was assumed that the process is adiabatic i.e. no heat transfer occurred through walls. The flow model used was viscous, compressible airflow [1, 6-10]. The following series of equations were used to solve a compressible turbulent flow for airflow simulation [1,6-12] ... 

Compilation of vapor pressures of organic and related compounds to one atmosphere. 

Standard conditions of femperature and pressure are commonly defined as 60°F (298K) and one atmosphere (14.7 psia or 101.3 kPa). 

The previous equation is only valid as long as there is no compositional change of the gas between the subsurface and the surface. The value of E is typically in the order of 200, in other words the gas expands by a factor of around 200 from subsurface to surface conditions. The actual value of course depends upon both the gas composition and the reservoir temperature and pressure. Standard conditions of temperature and pressure are commonly defined as 60°F (298K) and one atmosphere (14.7 psia or 101.3 kPa), but may vary from location to location, and between gas sales contracts. 

In a normally pressured reservoir, the pressure is transmitted through a continuous column of water from the surface down to the reservoir. At the datum level at surface the pressure is one atmosphere. The datum level for an offshore location is the mean sea level (msl), and for a onshore location, the ground water level. 

In abnormally pressured reservoirs, the continuous pressure-depth relationship is interrupted by a sealing layer, below which the pressure changes. If the pressure below the seal is higher than the normal (or hydrostatic) pressure the reservoir is termed overpressured. Extrapolation of the fluid gradient in the overpressured reservoir back to the surface datum would show a pressure greater than one atmosphere. The actual value by which the extrapolated pressure exceeds one atmosphere defines the level of overpressure in the reservoir. Similarly, an underpressured reservoir shows an pressure less than one atmosphere when extrapolated back to the surface datum. 

It is widely believed that gases are virtually ideal at a pressure of one atmosphere. This is more nearly tnie at relatively high temperatures, but at the nonnal boiling point (roughly 20% of the Boyle temperature), typical gases have values of pV/nRT that are 5 to 15% lower than tlie ideal value of unity. 

If the triple point pressure of a solid is below one atmosphere, it will melt if the heating is conducted rapidly so that the vajiour pressure can exceed that at the triple point. If camphor is heated in a closed space, the vapour pressure increases and when the value of 360 mm. is reached, the solid will melt further heating results in an increase in the vapour pressure and the camphor will boil when the vapour pressure is 760 mm. 

At normal pressures (around atmospheric) and up to about 250°C (approaching the limit of thermal stability for most organic compounds), a volatile substance can be defined as one that can be vaporized by heat between ambient temperature (10 to 30°C) and 200 to 250°C. All other substances are nonvolatile. 

Below One Atmosphere Pressure II, Afgon, Tech. ReportNo. 2, ContractNo. CST-7238, U.S. National Bureau ofStandards, Boulder, Colo.,June 1962. 

Note the error here is 3.8 percent, a value above the average. If the vapor pressure point available would have been closer to one atmosphere, the error would have been much lower. 

Enthalpy of Fusion The enthalpy (heat) of fusion AiTfus is defined as the difference of the enthalpies of a unit mole or mass of a solid and hquid at its melting temperature and one atmosphere pressure of a pure component. There are no generally apphcable estimation techniques that are very accurate. However, if the melting temperature is known, the atomic group contribution method of Chickos et al. " yields approximate results ... 

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