Benzene vapour pressure/boiling point

Solubility-. Very slightly soluble in water (0.05% by volume) miscible with benzene, chloroform, diethyl ether, carbon disulfide and ethanol (Budavari, 1996) Vapour pressure 12 kPa at 20°C relative vapour density (air = 1), 5.3 at the boiling-point (American Conference of Governmental Industrial Hygienists, 1991)... 

Van Wijk and Seeder s viscosity equation, 91 vapour, density of saturated, 324 specific heat of saturated, 336, 346-7, 359 vapour pressure 226 alignment chart, 271 of aliphatic esters, 286 of alkali halides, 237,243 of benzene, 267 boiling-point method for, 235 in capillary tubes, 367 of carbon, 246 centri fugal force, effect of, on 292 constant, 335, 341 over curved surface, 366 determination of, 227-47 dew-point method, 241 of dibasic acids, 243 dynamical method, 235 effusion method, 241. electrification, effect of on, 238, 375 of elements 257 of esters, 250 f., 286 of fusible metal, 230 in... 

Fischer on evaporation. The details of the mctfiod, bcin chiefly of pure physical interest, laeed only be I)i iefly referred to the observations were on the maximal vapour pressure of benzene they were carried out l)y Ra-msay by the so-called dynamic method—i.e. by debu minin the boiling point under constant pressure by. Fiseluir by tlu so-called static method—i.e. by observations of m smre at known temperatures. The results are given in millimetres of mercury —... 

In order that one may obtain the partial pressures (Fig. 43, series I) for such calculations of vapour compositions, both vapour pressure curves are plotted and the sunimated curve for the two partial pressures is drawn, as has been done for water and benzene in Fig. 39. At 760 miii a boiling point of 69.0°C is found for the mixture. -According to fonnula (40) the composition of the vapour is... 

Some polymerizable esters can be used as a copolymerizable internal plasticizer in technical applications. The best known of the group is diallyl phthalate (DAP), which is used to replace styrene, divinyl benzene, or methyl methacrylate in unsaturated polyester resins. It has a very low vapour pressure (300°C boiling point), leading to significant reduction in loss through evaporation. It considerably improves properties such as hardness, chemical resistance, hydrolysis resistance, electrical properties, and product life. It is particularly used in electrical applications, can be employed (after suitable preparation) in cold-cure systems, and shows high affinity to glass fibre. DAP can also be used as a reactive plasticizer with PVC resins. 

For example, a mixture of benzene and alcohol containing a mole fraction of alcohol of 0.46 has a vapour phase of equal composition, when the pressure is 1 atm. The first relation above, states that the boiling-point of the mixture will pass through either a maximum or a minimum at this composition (actually a minimum). Similarly, the second relation states that the total vapour pressure, at constant temperature, will pass through a maximum or a minimum at the same composition (actually a maximum). 

The second stage of the styrene process involves the dehydrogenation of ethylbenzene. The reaction is carried out in the vapour phase at temperatures of 600—650°C over catalysts based on either ferric or zinc oxides with lesser amounts of other metallic oxides such as chromic, cupric and potassium oxides. The reaction is favoured by low pressure and in order to reduce the partial pressure of the ethylbenzene the feed is mixed with superheated steam before passage over the catalyst. Normally, a conversion of 35—40% per pass is achieved. The product is cooled and allowed to separate into two layers the aqueous layer is discarded. The organic layer consists of styrene (about 37%), ethylbenzene (about 61%) and benzene, toluene and tar (about 2%). The separation of styrene by distillation is difficult because of the susceptibility of the monomer to polymerization at quite moderate temperatures and because the boiling point of styrene (145°C) is rather close to that of ethylbenzene (136°C). It is necessary therefore to use specially designed columns and to add a polymerization inhibitor (commonly sulphur) before distillation and to distil under reduced pressure. In a typical process, a four-column distillation train is used. In the first column benzene and toluene are removed at atmospheric pressure in the second and third columns ethylbenzene is removed at about 35 mm Hg in the fourth column styrene is separated from sulphur and tar, also at about 35 mm Hg. Finally, an inhibitor is added to the styrene t-butyl catechol is preferred for this purpose rather than sulphur which leads to discoloration of the final polymer. Styrene is a colourless liquid with a characteristic odour. 

Mixtures of Benzene with Alcohols.—Benzene is much more easily obtained in quantity than hexane, and behaves in a somewhat similar manner. The lower alcohols are miscible with benzene in all proportions but while methyl, ethyl, isopropyl, w-propyl, tertiary butyl and isobutyl alcohols form mixtures of maximum vapour pressure with that hydrocarbon, isoamyl alcohol does not, and it is practically certain that no alcohol of higher boiling point would form such a mixture. 

Benzene and Toluene.—In the case of benzene and toluene, the boiling points of mixtures have been found to agree very closely with those read from the theoretical curve, but the relation between the composition of liquid and vapour has not been experimentally determined. The mean ratio of the vapour pressures at temperatures between 80° and 110° is about 2 5, and we may probably assume that the relation is expressed with sufficient accuracy by the formula o b/ a = 2 5 Wb/ a ... 

M (gmol ) Osmotic pressure (mm benzene) Lowering of vapour pressure (mm Hg) Elevation of boiling point (K) Depression of freezing point (K)... 

If a mixture of benzene and toluene is heated in a vessel, closed in such a way that the pressure remains atmospheric and no material can escape and the mole fraction of the more volatile component in the liquid, that is benzene, is plotted as abscissa, and the temperature at which the mixture boils as ordinate, then the boiling curve is obtained as shown by ABCJ in Figure 11.5. The corresponding dew point curve ADEJ shows the temperature at which a vapour of composition y starts to condense. 

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