Toluene vapor pressure

Fig. 9.4. Typical tensimetric titration curve. Total pressure in the tensimeter is plotted against the mole ratio of BFj added to reactant. In this case the solvent was toluene which was maintained at — 78°C for each pressure measurement. The horizontal portion of the pressure curve originates from the low toluene vapor pressure at this temperature. Above the I i ratio of reactants, excess BFj is present and the pressure increases steadily with each addition of BFj.

The accuracy of the pressure and temperature measurements was verified by measuring the vapor pressure curves and critical points for pentane and for toluene. Vapor pressures were measured by observing the formation of a liquid phase as pentane or toluene was injected into the constant-volume view cell under isothermal conditions. The observation of critical opalescence was used to determine the critical point. The measured vapor pressures and critical points are given in Table I. Vapor pressures deviate from... 

Fig. 39. Fracture toughness Ki versus crack velocity in several partial toluene vapor pressures. O in air 0.5% mixture 0> 5% mixture the toughness is almost vapor pressure independent. From Ref., by permission of the publishers, Butterworth and Co. Ltd.

The physical piopeities of toluene have been well studied expeiimentally. Several physical properties ate presented in Table 1 (1). Thermodynamic and transport properties can also be obtained, from other sources (2—7). The vapor pressure of toluene can be calculated as follows (8), where P is in kPa and T is in K. 

The equilibrium vapor pressure of a flammable hquid at its closed-cup flash point about equ s its LFL in percent by volume. Thus, the vapor pressure of toluene at its closed-cup flash point (4.4°C or 40°F) of 1.2 percent (1.2 kPa) is close to its LFL of 1.1 percent. The composite LFL of a mixture may be estimated by Le Cnatelier s Rule ... 

Pressure affects flash point. A decrease in pressure lowers the flash point. With toluene, for example, at two-thirds of an atmosphere the vapor pressure must be only 0.74 kPa (5.6 mm Hg) to equal the LFL of 1.1 percent. (No significant difference in LFL will exist at two-thirds of an atmosphere compared to the published LFL of 1.1 percent at one atmosphere.) This vapor pressure occurs at —3°C, corresponding to a decrease in flash point of about 7.4°C from one atmosphere. Conversely, an increase in pressure raises the flash point. 

Toluene is a notoriously poor electrical conductor even in grounded equipment it has caused several fires and explosions from static electricity. Near normal room temperature it has a concentration that is one of the easiest to ignite and, as previously discussed, that generates maximum explosion effects when ignited (Bodurtha, 1980, p. 39). Methyl alcohol has similar characteristics, but it is less prone to ignition by static electricity because it is a good conductor. Acetone is also a good conductor, but it has an equihbrium vapor pressure near normal room temperature, well above UFL. Thus, acetone is not flammable in these circumstances. 

In extractive distillation, the compounds which it is desired to separate are distilled in the presence of a solvent. This solvent, by reason of its greater affinity for one of the compounds, causes the other material present to exhibit an abnormally high vapor pressure which permits its removal from the system. For example, adding phenol to a mixture of toluene and close-boiling paraffins and naphthenes causes the toluene to behave as if it boiled as much as 40 °F above its normal boiling point. 

Using the vapor pressure data for benzene and toluene [59] ... 

It is desired to separate a non-volatile material from an equimolal mixture of benzene, toluene, and xylene at 80°C. Vapor pressure data for these compounds are shown in several physical property sources. The following approximate values for the specific heats and latent heats of vaporization may be used ... 

Consider an ideal binary mixture of the volatile liquids A and B. We could think of A as benzene, C6H6, and B as toluene (methylbenzene, C6H< CH ), for example, because these two compounds have similar molecular structures and so form nearly ideal solutions. Because the mixture can be treated as ideal, each component has a vapor pressure given by Raoult s law ... 

What is the vapor pressure of each component at 25°C and the total vapor pressure of a mixture in which one-third of the molecules are benzene (so Xben/ene,liquid = 3 and xtoiuene,iiqUid = ) The vapor pressures of benzene and toluene at 25°C are 94.6 and 29.1 Torr, respectively. 

Self-Test 8.16B What is the total vapor pressure at 25°C of a mixture of equal masses of benzene and toluene ... 

The vapor of the mixture is richer than the liquid in the more volatile component (the component with the greater vapor pressure). Benzene, for instance, is more volatile than toluene, and so we can expect that the vapor in equilibrium with the liquid mixture will be richer in benzene than the liquid is. If we could express the composition of the vapor in terms of the composition of the liquid, we could confirm that the vapor is richer than the liquid in the more volatile component. 

Self-Test 8.17A (a) Determine the vapor pressure at 25°C of a solution of toluene in benzene in which the mole fraction of benzene is 0.900. (b) Calculate the mole fractions of benzene and toluene in the vapor. 

The normal boiling point of a binary liquid mixture is the temperature at which the total vapor pressure is equal to 1 atm. If we were to heat a sample of pure benzene at a constant pressure of 1 atm, it would boil at 80.1°C. Similarly, pure toluene boils at 110.6°C. Because, at a given temperature, the vapor pressure of a mixture of benzene and toluene is intermediate between that of toluene and benzene, the boiling point of the mixture will be intermediate between that of the two pure liquids. In Fig. 8.37, which is called a temperature-composition diagram, the lower curve shows how the normal boiling point of the mixture varies with the composition. 

Benzene, C6Hh, and toluene, C(,H5CH5, form an ideal solution. The vapor pressure of benzene is 94.6 Torr and that of toluene is 29.1 Torr at 25°C. Calculate the vapor pressure of each of the following solutions and the mole fraction of each substance in the vapor phase above those solutions at 25°C ... 

Fig. 111.—Experimental values of the interaction parameter %i plotted against the volume fraction of polymer. Data for polydi-methylsiloxane M =3850) in benzene, A (New-ingi6). polystyrene in methyl ethyl ketone, (Bawn et aV ) and polystyrene in toluene, O (Bawn et alP) are based on vapor pressure measurements. Those for rubber in benzene, T (Gee and Orr ) were obtained using vapor pressure measurements at higher concentrations and isothermal distillation equilibration with solutions of known activities in the dilute range.

Vapor Pressure Osmometry - The number average molecular weights of polymers with Mn < 20,000 were determined using "Model 232A Molecular Weight Apparatus, Wescan Instruments, Inc., 3018 Scott Blvd., Santa Clara, CA 95050". Toluene was used as solvent and the instrument was calibrated using polystyrene of Mn 9,000 and 20,400. 

The second stage of treatment is assumed to follow an exponential decrease in removal rates. Applying the approach of Kuo, this stage is divided into two time intervals, T2A and T2 2, representing the successive removal of equivalent amounts of toluene, Miem2A = Mrem2 2 = 2.3151. The initial theoretical concentration in the gas phase for the time interval T2A is equal to the vapor pressure of toluene, Ca = 109 mg/L. The final vapor concentration for this interval Ca f can be calculated from the total residual concentration Ctf and the phase distribution equations 5 and 7-9 in Table 14.3 ... 

A reboiler of a distillation column is required to supply 10 kg-s 1 of toluene vapor. The column operating pressure at the bottom of the column is 1.6 bar. At this pressure, the toluene vaporizes at 127°C and can be assumed to be isothermal. Steam at 160°C is to be used for the vaporization. The latent heat of vaporization of toluene is 344,000 J-kg 1, the critical pressure is 40.5 bar and critical temperature is 594 K. Steel tubes with 30 mm outside diameter, 2 mm wall thickness and length 3.95 m are to be used. The film coefficient (including fouling) for the condensing steam can be assumed to be 5700 Wm 2-K 1. Estimate the heat transfer area for ... 

Assume that the mixture of benzene and toluene obeys Raoult s Law and the molar mass in kilograms occupies 22.4 m3 in the vapor phase at standard conditions. The molar masses of benzene and toluene are 78 and 92 respectively. The vapor pressures of benzene and toluene at 25°C are 0.126 bar and 0.0376 bar respectively. 

It can be assumed that the molar mass in kilograms occupies 22.4 m3 at standard conditions. The molar mass of acetone can be taken to be 58 kg-kmol 1 and toluene 92 kg-kmoR1. The vapor pressure of acetone is given by ... 

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