Saturated vapour, density

Salt-hydrates, 379, 427 Sarrau s principle, 251 Saturated vapour, density of, 179 Saturation curve, 210 Schistic process, 32 Second law of thermodynamics, 39, 51, 52, 68, 73, 86, 112 Semipermeable septa, 272, 279,... 

Saturated vapour concentration Specific gravity Vapour density (air = 1) Solubility in water... 

It has often been supposed that at very high temperatures all gases would behave normally, i.e., would approach a limiting ideal state. As a matter of fact the deviations appear to be influenced by the density of the gas, and disappear at infinitely small densities whatever the temperature may be. Thus a saturated vapour at very low temperatures may behave like a permanent gas, on account of its very small density. 

The methods used for the determination of the density of a saturated vapour will be found in the treatises on Physics (cf. Young, Zeitschr. Physikal. Chem., 70, 620, 1910, who also finds the very simple relation ... 

At very low temperatures the pressures of the saturated vapours of liquids and solids are very small, and since the deviation of an actual gas from the laws of ideal gases becomes all the less the smaller is its density ( 70), we can safely assume that the vapour obeys the gas laws. 

From steam tables, at 4 bar saturation temperature 143.6°C, liquid density 926.4 kg/m3, vapour density 2.16 kg/m3. 

The most frequently used calibration procedure is based on temperature dependence of pressure of saturated mercury vapour [19,39-41]. At 25°C this pressure is of 0.0018 mm Hg height it corresponds to the vapour density of 20 pg/1. To get in the measurement cell a mercury concentration of about 10 ng/1, the saturated vapour should be strongly diluted. Instead of dilution, a lower temperature can be used however, the density of saturated vapour of 10 ng/1 corresponds to the temperature of less than —40°C. Both dilution and temperature decrease can be realized easily in laboratory conditions but their incorporation into a miniaturized chemical sensor is rather complicated. An attempt to develop such a device is reported in Ref. [41]. An additional problem in application of these techniques in portable sensing devices with integrated calibration is the necessity to have a reservoir with mercury in the device it complicates recycling of these devices and does not correspond to modern trends in technology. 

P9 Density evaluated at 90% of the saturation (vapour) pressure at inlet temperature, T), after a flash calculation. For a multicomponent mixture, use the bubble point pressure at T). The flash calculation should preferably be carried out isentropically, but an isenthalpic flash is sufficient CO E D)... 

Determination of pure component parameters. In order to use the EOS to model real substances one needs to obtain pure component below its critical point, a technique suggested by Joffe et al. (18) was used. This involves the matching of chemical potentials of each component in the liquid and the vapour phases at the vapour pressure of the substance. Also, the actual and predicted saturated liquid densities were matched. The set of equations so obtained was solved by the use of a standard Newton s method to yield the pure component parameters. Values of exl and v for ethanol and water at several temperatures are shown in Table 1. In this calculation vH and z were set to 9.75 x 10"6 m3 mole"1 and 10, respectively (1 ). The capability of the lattice EOS to fit pure component VLE was found to be quite insensitive to variations in z (6[Pg.90]

In figure (9), the curves VC and LC show the plots of the densities of saturated vapours and those of liquid against the corresponding temperatures. The point C, where the two curves meet gives the critical temperature. This point is not sharp as the curve in this range is rather flat. 

D is the density of the denser phase, and d that of the lighter, throughout this chapter. If the liquid is taken in contact with air, d is the density of air if in a vacuum, d is the density of the saturated vapour at the temperature of the experiment. In these cases d may often be neglocted without serious loss of accuracy. The equations also apply to interfaces between two liquids in which case d is the density of the lighter liquid. 

The formula of Cailletet and Mathias 2 gives the mean isobarie densities of a liquid and its saturated vapour as a rectilinear function of the temperature. Thus... 

Determination of Critical Volume In the determination of critical volume, advantage is taken of the observation made by Cailletet and Mathias that when the mean densities of liquid and saturated vapour of a substance are plotted against the corresponding temperature of a substance a straight line is obtained. 

The same apparatus was used for the determination of the densities of saturated vapour, in which case both liquid and vapour were present in the tube ( 4.VIII H). 

The densities of liquids near the critical temperature increase with molecular weight in homologous series, but the critical densities do not, hence there must be an inversion with increase of temperature. The ratios of the densities of the higher, tp. those of the lower members of such series increase regularly with temperature.7 The ratio of the densities of the saturated vapours first decreases with temperature and then increases the ratios of the densities of liquid and saturated vapour at a given temperature increase with the molecular weight in homologous series. 

By using values for the densities of saturated vapour found by Schoop, Schumann found satisfactory agreement with Winkehnann s formula for the vapour pressures of aliphatic esters, whilst Duhring s formula gave very different specific factors. 

Schoop, with an apparatus similar to Herwig s, measured the densities of saturated vapours of benzene, methyl, ethyl, and propyl formates, methyl and ethyl acetates, and methyl propionate, and confirmed equation (2) up to 60°, beyond which the constant diminished for methyl acetate ... 

P6rot5 determined the densities of saturated vapours by exposing a vacuous globe to the vapour, closing it when full of vapour, and weighing after cooling. Bauer used Archimedes principle, weighing a float in the vapour. 

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