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	Vapor pressure - Wikipedia, the free encyclopedia
		The vapor pressure is the pressure (if the vapor is mixed with other gases, the partial pressure) of a vapor(this vapour being formed from from molecules/atoms escaping from a liquid/solid).
		This is the equilibrium vapor pressure or saturation vapor pressure of that substance at that temperature.
		The term vapor pressure is often understood to mean the saturation vapor pressure.
	en.wikipedia.org /wiki/Vapor_pressure (412 words)

	VAPORIZATION - LoveToKnow Article on VAPORIZATION (Site not responding. Last check: 2007-10-09)
		Supposing that the external pressure and temperature remain constant, the partial pressure of the gas inside the bubble varies inversely as the volume of the bubble, and may be represented by a/ri.
		The tota/ heat of the saturated vapour at any temperature is usually defined as the quantity of heat required to raise unit mass of the liquid from any convenient zero up to the temperature considered, and then to evaporate it at that temperature under the constant pressure of saturation.
		The pressure under which the liquid is heated makes very little difference to the quantity h, but, in order to make the statement definite, it is desirable to add that the liquid should be heated under a constant pressure equal to the final saturation-pressure of the vapour.
	www.1911encyclopedia.org /V/VA/VAPORIZATION.htm (9992 words)

	SQUARE ONE : Vapour Pressure (Site not responding. Last check: 2007-10-09)
		Just as air pressure is directly related to the number of gas molecules per cubic metre of space, so vapour pressure results from the number of water vapour molecules per cubic metre.
		If the vapour pressure in the air is already very high, it is more difficult for water molecules to break free from a liquid surface and enter the air as vapour.
		As the vapour pressures are set by the quantities of vapour in the air, the relative humidity is also given by the ratio between the actual vapour pressure and the saturation vapour pressure at the same temperature.
	www.squ1.com /comfort/vapour-pressure.html (483 words)

	saturated vapour pressure - an introduction
		This pressure is called the saturated vapour pressure (also known as saturation vapour pressure) of the liquid.
		The saturated vapour pressure of this liquid at the temperature of the experiment is 130 mmHg.
		Water's saturated vapour pressure is about 20 mmHg at this temperature.
	www.chemguide.co.uk /physical/phaseeqia/vapourpress.html (1460 words)

	The gas laws and anesthesia
		water and water vapour, the concentration of the latter in the air is known as humidity).
		This is because the pressure inside the syringe is increasing due to compression of air.
		If the pressure in the container is doubled, then the amount of gas dissolved is also doubles, but because of Boyles law (V 1/P), the volume of gas dissolved is halved, so the said volume is the same as it was initially, even though there are twice as many molecules dissolved.
	www.4um.com /tutorial/science/gas1.htm (1268 words)

	DW(i+at)X587 - Online Information article about DW(i+at)X587
		pressure, WI the weight in water, atmospheric conditions remaining very nearly the same; p is the density of the water in which the body is weighed, a is (1 +at°) in which a is the coefficient of cubical expansion of the body, and S is the density of the air at t°, p mm.
		expulsion method, the vapour always mixes to some extent with the air in the tube, and this involves a reduction of the pressure of the vapour.
		process in which the increase of pressure due to the volatilization of the substance, and not the volume of the expelled air, is measured.
	encyclopedia.jrank.org /DRO_ECG/DW_iat_X587.html (3158 words)

	STOICHIOMETRY - LoveToKnow Article on STOICHIOMETRY (Site not responding. Last check: 2007-10-09)
		Gases.The generalization due to Avogadrothat equal volumes of gases under the same conditions of temperature and pressure contain equal numbers of moleculesmay be stated in the form that the densities of gases are proportional to their molecular weights.
		The measuring tube is surrounded by an outer tube which has an exit to a condenser at the side or bottom, communication being made between the measuring tube and jacket by a small hole near the top of the former.
		Other methods are available for dissolved substances such as measurements of the osmotic pressure, lowering of the vapour pressure and diminution of solubility, but these are little used.
	www.87.1911encyclopedia.org /S/ST/STOICHIOMETRY.htm (3883 words)

	Chapter 3 - Meteorological data
		Due to the non-linearity of humidity data required in the FAO Penman-Monteith equation, the vapour pressure for a certain period should be computed as the mean between the vapour pressure at the daily maximum and minimum air temperatures of that period.
		The actual vapour pressure of the air is the saturation vapour pressure at the dewpoint temperature, The drier the air, the larger the difference between the air temperature and dewpoint temperature.
		The vapour pressure is commonly derived from relative humidity or dewpoint temperature.
	www.fao.org /docrep/X0490E/x0490e07.htm (9079 words)

	CANUTEC - Articles English - Vapour Pressure (Site not responding. Last check: 2007-10-09)
		The vapour pressure is the pressure at which a liquid and its vapour are in equilibrium at a given temperature.
		When the vapour pressure reaches the atmospheric pressure, the liquid is at its boiling point.
		Vapour pressure is measured in units of atmospheres (atm), millimeters of mercury (mmHg) or kilopascals (kPa).
	www.tc.gc.ca /canutec/en/articles/documents/vapour.htm (907 words)

	AERADE subject listing for Vapour pressure. Halogenated aliphatic hydrocarbons.
		The coefficients of the equation are given for each compound and three tables of vapour pressure values calculated using them are included: in SI units at 5 K and 10 K intervals, in atmospheres at 5 and 10 C intervals, in lbf/sq in at 10 F intervals.
		The coefficients of the equation are given for each compound and three tables of vapour pressure values calculated using them are included: in SI units at 5 K and 10 K intervals, in atmospheres at 5 and 10 degree C intervals, in lbf/sq in at 10 and 20 degree F intervals.
		The coefficients for the equation are given for each compound and three tables of vapour pressure values calculated using them are included: in SI units at 5 K and 10 K intervals, in atmospheres at 5 and 10 degree C intervals, in lbf/sq in at 10 degree F intervals.
	aerade.cranfield.ac.uk /subject-listing/esdu/ES22.html (740 words)

	AERADE subject listing for Vapour pressure. General. Aliphatic hydrocarbons (Site not responding. Last check: 2007-10-09)
		After sections on units and the importance of purity of samples used for measurement of vapour pressure, the general shape of the vapour-pressure curve is discussed.
		Vapour pressure is highly dependent on temperature and evaluation of data invariably involves fitting to an equation relating pressure to temperature; selected equations are listed and recommendations given.
		The coefficients of the equation are given for each compound and three tables of vapour pressure are included: in SI units at 5 K intervals, in atmospheres at 5 degree C intervals and in lbf/sq in at 10 degree F intervals.
	aerade.cranfield.ac.uk /ROADS/subject-listing/esdu/ES17.html (890 words)

	ipedia.com: Vapor pressure Article (Site not responding. Last check: 2007-10-09)
		The vapor pressure is the pressure of a vapor.
		At any given temperature, for a particular substance, there is a pressure at which the vapor of that substance is in equilibrium with its liquid or solid...
		When the partial pressure equals the vapor pressure of any liquid, the liquid and vapor are in equilibrium.
	www.ipedia.com /vapor_pressure.html (459 words)

	Vapour Pressure and Humidity (Site not responding. Last check: 2007-10-09)
		When air holds the maximum possible amount of vapour, the vapour exerts what is called the saturation vapour pressure.
		The ratio of actual pressure to the saturation vapour pressure at any given temperature, expressed as a percentage, is called the relative humidity (rh).
		the rate of evaporation is dependant on the difference between the vapour pressure exerted by the wet wood surfaces and that of the air/water vapour mixture in immediate contact with them (Pratt 1974).
	sres.anu.edu.au /associated/fpt/drying/vapour.html (125 words)

	[No title] (Site not responding. Last check: 2007-10-09)
		At equilibrium, the pressure exerted by the molecules evaporated from the liquid is termed the vapour pressure of that substance.
		The temperature at which the vapour pressure of a liquid equals the total pressure is termed the boiling point at that pressure.
		When the total pressure above a liquid is greater than the vapour pressure at the temperature of the liquid, some other gas (eg air) must be exerting the pressure additional to the vapour pressure of the liquid.
	www.fie.com.au /uqfoodengineering/3vapliqsteam.doc (1695 words)

	Moisture in air
		The Relative Humidity (RH) is the ratio of the actual water vapour pressure to the saturation water vapour pressure at the prevailing temperature.
		, the saturation vapour pressure at the ambient temperature.
		The water vapour pressure is 1500 Pa. The water vapour concentration in kg/m3 is 0.011, in kg/kg it is 0.009.
	www.natmus.dk /cons/tp/atmcalc/atmoclc1.htm (1541 words)

	Vapour pressure of ice at temperatures between —100 and 0 °C 3.4.1
		The plot of the logarithm of vapour pressure p against the reciprocal of Kelvin temperature T for a single substance is usually nearly linear and may be used for interpolation and, with caution, for extrapolation.
		For substances other than water, vapour pressures are either not known with sufficient accuracy or are not given here with sufficient precision for specification of the temperature scale to be significant.
		The vapour pressure of a substance may be affected by the presence of other substances.
	www.kayelaby.npl.co.uk /chemistry/3_4/3_4_1.html (282 words)

	CSA - NEEMO - The Vapour Pressure of Water
		The vapour pressure within a liquid depends upon the temperature of the liquid.
		At this temperature the vapour pressure of molecules (within the water) causes the rapid and often violent formation of bubbles within the water.
		Boiling occurs whenever the vapour pressure of the molecules within the water equals (or exceeds) the local atmospheric pressure.
	www.space.gc.ca /asc/eng/educators/resources/neemo/gases/water.asp (249 words)

	ENTHALPY OF VAPORISATION OF WATER
		To determine the enthalpy of vaporisation of water from the measurement of vapour pressure at various temperatures.
		The number of moles of air in the mixture can be found by reducing the temperature of the whole apparatus to about 5 C. At that temperature it can be assumed that the vapour pressure of water is so small that the volume of gas measured corresponds only to the air present.
		Assume that the vapour pressure of water is negligible compared to atmospheric pressure at the low temperature.
	wwwchem.uwimona.edu.jm:1104 /lab_manuals/c10p5.html (647 words)

	Vapour Pressure (Site not responding. Last check: 2007-10-09)
		When a liquid is exposed to atmosphere molecules escape from its surface in a vapour form.
		Supposing the liquid is placed in a closed container, the activity continues so that vapour fills the space in between the liquid level and the container.
		The pressure it exerts upon the liquid surface is the vapour pressure.
	www.ae.su.oz.au /aero/fprops/propsoffluids/node15.html (54 words)

	Chem2OA3 - Experiment 2 - Isolation of Natural Products
		The boiling point of a liquid is that temperature at which the vapour pressure of the liquid is equal to the pressure of its surroundings.
		The vapour pressure of a pure liquid rises steadily as the temperature is increased, until the boiling point is reached (Figure 1).
		The thermometer should be placed in the vapour of the boiling liquid (the thermometer bulb is positioned midway in the opening of the condenser) to record the boiling point, which should remain constant throughout the distillation.
	www.chemistry.mcmaster.ca /~chem2oa3/labmanual_2002-03/2oa3_exp2.html (3338 words)

	Raoults Law and phase diagrams (Site not responding. Last check: 2007-10-09)
		The vapour pressure/ composition diagram is plotted at constant temperature; a series of these plots at different temperatures (fig 1, right) is needed in order to obtain a boiling point/composition diagram.
		Since vapour pressure does not increase linearly with an increase in temperature, the vapour pressure lines at the different temperatures are not parallel.
		The link between the vapour pressure/composition and boiling temperature/composition diagrams for non-ideal (azeotropic) mixtures is the same, but such systems give a more complex diagram because of the vapour pressure maximum or minimum.
	www.rod.beavon.clara.net /raoult.htm (342 words)

	Raoult's Law and ideal mixtures of liquids
		The partial vapour pressure of a component in a mixture is equal to the vapour pressure of the pure component at that temperature multiplied by its mole fraction in the mixture.
		The vapour pressure of pure methanol at this temperature is 81 kPa, and the vapour pressure of pure ethanol is 45 kPa.
		Notice that the vapour pressure of pure B is higher than that of pure A. That means that molecules must break away more easily from the surface of B than of A. B is the more volatile liquid.
	www.chemguide.co.uk /physical/phaseeqia/idealpd.html (2379 words)

	AERADE subject listing for Vapour pressure. Polycyclic compounds. (Site not responding. Last check: 2007-10-09)
		Where the data were less extensive or reliable, it was found possible to develop a correlation using a method that relates the second differential of the Wagner vapour pressure equation to the difference between the ideal gas and the liquid heat capacities.
		The coefficients of the equation are given for each compound and two tables of vapour pressure values calculated using them are included: in SI units at 5 K intervals and in mm of mercury or atmospheres (for the higher values) at 5 degree Celsius intervals.
		The data available were limited but using a correlation previously developed for the alkanes that relates the second differential of the Wagner vapour pressure equation to the difference between the ideal gas and liquid heat capacities extrapolation was possible.
	www.aerade.aero /subject-listing/esdu/ES218.html (417 words)

	[No title] (Site not responding. Last check: 2007-10-09)
		The maximum amount of water vapour, that air can contain, depends on the temperature and, for certain temperature ranges, also on whether the air is near to a water or ice surface.
		Vapor pressure (e) is the fraction of the ambient pressure that is due to the fraction of water vapor in the air.
		Saturated vapor pressure (ES): ES = 6.1078 * 10 ** ((T * A)/(T + B)) \ temperature A = 7.5 } for use in B = 237.3 } vapor pressure with respect to water * A = 9.5 } for use in vapor pressure B = 265.5 } with respect to ice 3.
	cui.unige.ch /~luthi/download/dew.txt (1004 words)

	Chemical process engineering - Vapour Pressure for Mixtures (Site not responding. Last check: 2007-10-09)
		It is liquids that have vapour pressure which represents the equilibrium between the liquid and its vapor phase.
		Since you are speaking of a mix of gases, their partial pressures are the result of multiplying the total pressure by the individual mol fraction, assuming no association or otherwise intermolecular effects.
		His wording "vapour pressure" may be confusing since it hints at the presence of liquids.
	www.eng-tips.com /viewthread.cfm?qid=53610 (1960 words)

	Chemical process engineering - Vapour pressure and critical temperature
		When isothermally removing gas, the total pressure in the well drops and part of the nat-gas (butanes and heavier) liquefies, a fact that may lead to a reduction in the production of the well when the liquid is trapped in the sands.
		The upstream pressure of your control valve is not equivalent to the vapor pressure of the fluid.
		Usually "vapor pressure" refers to a the pressure imparted by a liquid in a tank or vessel and is a function of temperature.
	www.eng-tips.com /viewthread.cfm?qid=70867 (1085 words)

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