Hydroquinone, vapor pressure

Table III shows the vapor pressures of some hydroquinone clathrates at 25°C calculated according to Eq. 38, and Table IV...

When studying heterogeneous equilibria involving clathrates, one is faced with peculiar difficulties owing to the hysteresis effects mentioned in the introduction the solute in a clathrate crystal of hydroquinone, for instance, will not come to thermodynamic equilibrium with the vapor in which it is placed. Consequently it is impossible, or at least very difficult, to measure the equilibrium vapor pressure of the solute in a clathrate by placing some crystals in a tensometer (cf. the experiments of Wynne-Jones and Anderson,58 and those of Leech and Richards reported by Powell33). 

The equilibria between clathrate and gas, and Qa, clathrate, and gas could be determined by using w-propanol as the auxiliary solvent.53 In the latter equilibrium, the composition of the clathrate is found from the amount of gas required for the conversion of a given amount of solid a-hydroquinone suspended in the propanol solution into clathrate at constant temperature and pressure. The dissociation pressure of the clathrate is given by the total pressure of the four-phase equilibrium -clathrate-solution-gas, corrected for the vapor pressure of w-propanol saturated with a-hydroquinone. Using this technique it was found that the equilibrium clathrates of hydroquinone and argon have yA = 0.34 at 25°C63 and 0.28 at 60°C.28... 

Hydroquinone could occur in air at ambient temperature as particulates and not vapor, as its vapor pressure is too low. 

Reported vapor pressures of hydroquinone coefficients for the vapor pressure equations (1,4-dihydroxybenzene) at various temperatures and the... 

FIGURE 14.1.4.7.1 Logarithm of vapor pressure versus reciprocal temperature for hydroquinone. 

Bender, R., Bieling, V., Maurer, G. (1983) The vapor pressures of solids anthracene, hydroquinone, and resorcinol. J. Chem. Thermodyn. 15, 585-594. 

Combustible liquid Hash point (open cup) 48°C (118°F) vapor pressure 3.2 torr at 20°C (68°F) autoignition temperature 293°C (559°F) vapor forms explosive mixtures with air within the range 1.5-9.9% by volume in air. n-Butyl acrylate may polymerize at elevated temperature. The reaction is exothermic and may cause pressure buildup and violent rupture of closed containers. The polymerization may be prevented by 40-60 ppm of hydroquinone or its monomethyl ether. Its reactions with strong oxidizers can be vigorous to violent. 

Definition Monomethyl ether of hydroquinone Empiricai C7H8O2 Formuia CH3OC6H4OH Properties Colorless to wh. waxy solid or cryst. powd. caramel/phenol odor sol. in water, benzene, ether, acetone, ethyl acetate, alcohol, oxygenated soivs. m.w. 124.14 dens. 1.55 (20/20 C) vapor pressure < 0.01 mm Hg (20 C) m.p. 

In a 500-cc. flask fitted with a 24-cm. fractionating column (Notes 1 and 4) attached to a water-j acketed condenser, are placed 148 g. (1 mole) of dry powdered cinnamic acid, 2 g. of hydroquinone and several small pieces of day plate. One-half gram of hydroquinone is also placed in the flask in which the distillate is to be collected (Note 2). The acid is rapidly heated over a wire gauze with a free flame until phenylethylene begins to distil, the heating being regulated so that the temperature of the vapors at the head of the column never exceeds 130°, and mainly remains below 120° (Notes 3 and 4). The cinnamic acid refluxes, but very little should escape and collect in the condenser. The decomposition is complete in three and one-half to five hours, when no more phenylethylene distils and the temperature at the head of the column rises rapidly. The distillate consists of a straw-colored oil and a little water a dark tarry residue (50-60 g.) remains in the reaction flask. About 100 cc. of water is added to the distillate and the aqueous mixture is distilled. The phenylethylene is easily volatile with steam and separates in the distillate as a colorless oil. The oil (45-48 g.) is separated, dried with a small amount of calcium chloride, and carefully distilled under diminished pressure, cool-... 

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