Vapours, density

Figure A2.3.5 (a) PIpkT as a fimction of the reduced variables and and (b) coexisting liquid and vapour densities in reduced units pp as a fimction of Jp for several substances (after [19]).

Surface waves at an interface between two innniscible fluids involve effects due to gravity (g) and surface tension (a) forces. (In this section, o denotes surface tension and a denotes the stress tensor. The two should not be coiifiised with one another.) In a hydrodynamic approach, the interface is treated as a sharp boundary and the two bulk phases as incompressible. The Navier-Stokes equations for the two bulk phases (balance of macroscopic forces is the mgredient) along with the boundary condition at the interface (surface tension o enters here) are solved for possible hamionic oscillations of the interface of the fomi, exp [-(iu + s)t + i V-.r], where m is the frequency, is the damping coefficient, s tlie 2-d wavevector of the periodic oscillation and. ra 2-d vector parallel to the surface. For a liquid-vapour interface which we consider, away from the critical point, the vapour density is negligible compared to the liquid density and one obtains the hydrodynamic dispersion relation for surface waves + s>tf. The temi gq in the dispersion relation arises from... 

This oxide was originally given the formula P2O5 and called phosphorus pentoxide but the vapour density and structure indicate the formula P40,q. It is prepared by burning phosphorus in a plentiful supply of air or oxygen ... 

Molecular Weight Determinations by Physical Methods. Vapour Density. Victor Meyer s Method. 

The liquid in B rapidly volatilises at the bottom of the tube T, the stopper being thrown off, and bubbles of air escape from D into the tube C. Continue boiling the liquid in J steadily until no more bubbles escape into C. Then carefully slip the end of D from under the tube C, close the end of C securely with the finger, and then transfer the tube to a gas-jar of water, so that the level of the water inside and outside C can be equalised. Measure the volume of air in C, and note the room temperature and the barometric pressure. The vapour density can now be calculated (see p. 428). 

Vapour Density of Carbon Tetrachloride, chlorobenzene being used as the heating liquid. 

Therefore Vapour Density = 79 and Molecular Weight = 158 Theoretical for CCl, 154. 

Physical characteristics Molecular weight Vapour density Specific gravity Melting point Boiling point Solubility/miscibility with water Viscosity Particle size size distribution Eoaming/emulsification characteristics Critical temperature/pressure Expansion coefficient Surface tension Joule-Thompson effect Caking properties... 

Adiponitrile (Tetramethylene cyanide) CN(CH,)4CN Can behave as a cyanide when ingested or otherwise absorbed into the body Combustion products may contain HCN Water-white, practically odourless liquid Elash point 93°C Specific gravity 0.97 Vapour density 3.7... 

Cyanogen (Ethane dinitrile, Prussite) (CN)2 Highly poisonous gas similar to HCN Colourless flammable gas with a pungent almondlike odour, becoming acrid in higher concentrations Water soluble Vapour density 1.8... 

Cyanogen bromide (Bromine cyanide) CNBr Extremely irritating and toxic vapours Contact with acids, acid fumes, water or steam can produce toxic and corrosive fumes Transparent crystals with a penetrating odour Melting point 52°C Boiling point 61 °C Vapour density 3.6 Water soluble... 

Cyanogen chloride (Chlorine cyanide) CNCI Poisonous liquid or gas Vapour highly irritating and very toxic Colourless liquid with a strong irritating smell Boiling point 1 3°C Vapour density 2.1... 

Halogen Melting point (°C) Boiling point (°C) Vapour density (air = 1.0) Threshold limit value (ppm) Reactivity and oxidizing strength Appearance and state at 21 " C Colour of gas/vapour... 

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

The density of a vapour or gas at eonstant pressure is proportional to its relative moleeular mass and inversely proportional to temperature. Sinee most gases and vapours have relative moleeular masses greater than air (exeeptions inelude hydrogen, methane and ammonia), the vapours slump and spread or aeeumulate at low levels. The greater the vapour density, the greater the tendeney for this to oeeur. Gases or vapours whieh are less dense than air ean, however, spread at low level when eold (e.g. release of ammonia refrigerant). Table 6.1 ineludes vapour density values. 

Ignition temperature Flammable limits Vapour density... 

R. Evans, J. R. Henderson, D. C. Hoyle, A. O. Parry, Z. A. Sabeur. Asymptotic decay of liquid structure oscillatory liquid-vapour density profiles and the Fisher-Widom line. Mol Phys 50 755-775, 1993. 

The vapour density of fieshly distilled aniline, b.p. 182 , may iDe determined, the temperatme of the air-bath being adjusted to about 240°. The adjustment is made by raising or loivermg the flame, or by altering the position of the movable ring burner. 

Y/acuum-desiccator, 45 Vacuum distillation, 84, 94 Vapour density method, 29 Vicior-Meyer Apparatus, 29... 

According to I lCeard, the principal consiituent is a ht drocarhnn of the empirical formula (C,ir.).r, which from a vapour density dctcr-in mation apjicQrs to bo... 

It will be noticed that we make no assumption as to the molecular weight of the solvent in the liquid state. Equation (8) refers to the vapour only. It is to be expected, therefore, that when the solvent does not yield a vapour having the normal density, the value of the molecular lowering will be abnormal. Raoult found that when acetic acid was used as solvent the observed molecular lowering was 0 0163. Acetic acid, however, is known to be polymerised in the state of vapour at the boiling-point the molecular weight as determined by the vapour density is 1 64 times the normal (C2H4O2 = 60). The number of mols per unit volume will be reduced in the same ratio, and hence we must write (3) ... 

In confirmation it was observed that such substances (e.g., acetic acid) gave abnormally high vapour densities. 

Premier and Schupp have made vapour-density measurements with sulphur enclosed in a quartz bulb heated electrically and connected with a manometer consisting of a spiral of silica tubing attached to a small mirror. The pressure was measured by the amount of unwinding of the spiral. The same method has been used by Bodenstein and Katavama in studving the equilibrium ... 

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,... 

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