High vapor pressure

The vapor pressure of a crude oil at the wellhead can reach 20 bar. If it were necessary to store and transport it under these conditions, heavy walled equipment would be required. For that, the pressure is reduced (< 1 bar) by separating the high vapor pressure components using a series of pressure reductions (from one to four flash stages) in equipment called separators , which are in fact simple vessels that allow the separation of the two liquid and vapor phases formed downstream of the pressure reduction point. The different components distribute themselves in the two phases in accordance with equilibrium relationships. 

Health and Safety Factors. Because of their high vapor pressures (methyl vinyl ether is a gas at ambient conditions), the lower vinyl ethers represent a severe fire hazard and must be handled accordingly. Contact with acids can initiate violent polymerization and must be avoided. Although vinyl ethers form peroxides more slowly than saturated ethers, distillation residues must be handled with caution. 

The ICC classifies all three pentanes as flammable Hquids and requires that they be affixed with a red label for shipping. Because of their high vapor pressures, n- and isopentane are transported in heavy-walled dmms and neo-pentanes are transported in cylinders (see Packaging containers and INDUSTRIAL MATERIALS). 

Halides. Indium trichloride [10025-83-8] InCl, can be made by heating indium in excess chlorine or by chlorinating lower chlorides. It is a white crystalline soHd, deUquescent, soluble in water, and has a high vapor pressure. InCl forms chloroindates, double salts with chlorides of alkaLi metals, and organic bases. 

Liquid Metals. If operating temperatures rise above 250—300°C, where many organic fluids decompose and water exerts high vapor pressure, hquid metals have found some use, eg, mercury for limited appHcation in turbines sodium, especially its low melting eutectic with 23 wt % potassium, as a hydrauhc fluid and coolant in nuclear reactors and potassium, mbidium, cesium, and gallium in some special uses. 

Mercuric Chloride. Mercuric c Aon.d.e.[7487-94-7] HgCl2, is also known as corrosive sublimate of mercury or mercury bichloride. It is extremely poisonous, and is particularly dangerous because of high (7 g/L at 25°C) water solubiUty and high vapor pressure. It sublimes without decomposition at 300°C, and has a vapor pressure of 13 Pa (0.1 mm Hg) at 100°C, and 400 Pa (3 mm Hg) at 150°C. The vapor density is high (9.8 g/cm ), and therefore mercuric chloride vapor dissipates slowly (5). 

Evaporation Retardants. Small molecule solvents that make up the most effective paint removers also have high vapor pressure and evaporate easily, sometimes before the remover has time to penetrate the finish. Low vapor pressure cosolvents are added to help reduce evaporation. The best approach has been to add a low melting point paraffin wax (mp = 46-57° C) to the paint remover formulation. When evaporation occurs the solvent is chilled and the wax is shocked-out forming a film on the surface of the remover that acts as a barrier to evaporation (5,6). The addition of certain esters enhances the effectiveness of the wax film. It is important not to break the wax film with excessive bmshing or scraping until the remover has penetrated and lifted the finish from the substrate. Likewise, it is important that the remover be used at warm temperatures, since at cool temperatures the wax film may not form, or if it does it will be brittle and fracture. Rapid evaporation occurs when the wax film is absent or broken. 

Alkylamiaes are toxic. Both the Hquids and vapors can cause severe irritations to mucous membranes, eyes, and skin. Protective butyl mbber gloves, aprons, chemical face shields, and self-contained breathing apparatus should be used by aH personnel handling alkylamiaes. Amines are flammable and the lower mol wt alkylamiaes with high vapor pressures at ordiaary temperatures have low flash poiats. Amines should be handled ia weH-veatilated areas only after eliminating potential sources of ignition. 

AH ammonium haUdes exhibit high vapor pressures at elevated temperatures, and thus, sublime readily. The vapor formed on sublimation consists not of discrete ammonium haUde molecules, but is composed primarily of equal volumes of ammonia and hydrogen haUde. The vapor densities are essentiaHy half that expected for the vaporous ammonium haUdes. Vapor pressures at various temperatures are given in Table 2 (11). Latent heats of sublimation, assuming complete dissociation of vapors and including heats of dissociation are 165.7, 184.1, and 176.6 kJ /mol (39.6, 44.0, and 42.2... 

Because of the high vapor pressure of the simple quinones and their penetrating odor, adequate ventilation must be provided in areas where these quinones are handled or stored. Quinone vapor can harm the eyes, and a limit of 0.1 ppm of 1,4-benzoquinone in air has been recommended. Quinone in either sohd or solution form can cause severe local damage to the skin and mucous membranes. Swallowing benzoquinones may be fatal the LD q in rat is 130 mg/kg orally and 0.25 mg/kg intravenously. There is insufficient data concerning quinones and cancer. The higher quinones are less of a problem because of their decreased volatihty (118—120). 

External floating roo cheaper to constmct than double deck for 5—50-m diameter suitable for high vapor pressure stocks capable of in-service repair of appurtenances good buoyancy... 

Batch distillation (see Fig. 3) typically is used for small amounts of solvent wastes that are concentrated and consist of very volatile components that are easily separated from the nonvolatile fraction. Batch distillation is amenable to small quantities of spent solvents which allows these wastes to be recovered onsite. With batch distillation, the waste is placed in the unit and volatile components are vaporized by applying heat through a steam jacket or boiler. The vapor stream is collected overhead, cooled, and condensed. As the waste s more volatile, high vapor pressure components are driven off, the boiling point temperature of the remaining material increases. Less volatile components begin to vaporize and once their concentration in the overhead vapors becomes excessive, the batch process is terrninated. Alternatively, the process can be terrninated when the boiling point temperature reaches a certain level. The residual materials that are not vaporized are called still bottoms. 

Phosphorus Pentoxide. This compound, P2O55 (Class 1, nonregenerative) is made by burning phosphoms ia dry air. It removes water first by adsorptioa, followed by the formation of several forms of phosphoric acid (2). Phosphoms peatoxide [1314-56-3] has a high vapor pressure and should only be used below 100°C. Its main drawback is that as moisture is taken up, the surface of the granules becomes wetted and further moisture removal is impeded. For this reason, phosphoms pentoxide is sometimes mixed with an iaert material (see Phosphoric acids and phosphates). 

The vapor pressure of a compound is important in determining the upper limit of its concentration in the atmosphere. High vapor pressures will permit higher concentrations than low vapor pressures. Examples of organic compounds are methane and benzo[fl]pyrene. Methane, with a relatively high vapor pressure, is always present as a gas in the atmosphere in contrast, benzo[fl]pyrene, with a relatively low vapor pres.surc, is. id-... 

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. 

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