Density liquid/vapour ratio

Cas Boiling point Liquid density Volume ratio gas Vapour Critical... 

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) ... 

Cas Boiling point at 7 bar a <°C) Liquid density at boiling point (kg/m1) Volume ratio of gas (1 bar a, 20°C) to liquid (at boiling point) Vapour pressure at 3BCC (bar abs.) Critical temperature <°C)... 

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. 

Although Pavlov supposed that, at a given temperature and pressure, unit volume of any liquid or solid contains an equal number of associated molecules, this is inconsistent with modern views on the liquid and solid states. Antonoff assumed that the number of molecules in unit volume in two phases in equilibrium is the same, and the degree of association is then equal to the ratio of the densities of the condensed and vapour phases for liquids the association factor may reach 10,000. Makovetzky put the real density q the following functions of the observed ( apparent ) density q ... 

Herz foimd that the ratios of the densities of liquid and vapour at equal fractions of the critical temperature are fairly constant in homologous series, but may vary from 7 to 12 for different classes of substances. He also found that Nernst s equation (33) ... 

This is the ratio between the molecular weight of the solvent and the molecular weight of air. Apart from methanol, which has the lowest vapour density of any liquid solvent, all organic solvents are appreciably denser. This means that spillages, whether on a small scale in the laboratory or on a large scale in transport or in an industrial plant, will give rise to vapour at a low level. Ventilation should therefore be designed to draw from this level and tests for flammable or toxic concentrations should be made at a low point. 

Physically, r is proportional to the ratio of mass transfer coefficient of liquid water in membrane to mass transfer coefficient of water vapour in the backing layer. The parameter r thus describes the competition of two opposite water fluxes back diffusion, which wets the anode side of the membrane and leakage through the backing layer to the channel, which facilitates membrane drying. Physically, r controls the local water-limiting current density (see below). 

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