Keywords: Gasoline additives; Vapor pressure; Octane number 1. Introduction The properties of commercial gasoline are influenced by the origin of the crude oil, the refinement processes and the presence of additives, which are added with the purpose of improving the performance and reducing the emissions of automotive vehicles . The addition of oxygenates to gasoline became widespread after the elimination of the tetraethyl lead compounds . Brazil was one of the pioneers in the removal of this compound through its substitution for alcohol ethanol.
The improved combus- tion achieved by using oxygenated additives alcohols and tertiary ethers in place of aromatic compounds has led to growing interest in the former . Methyl tert-butyl ether MTBE; 2-methoxymethyl- propane and ethanol are the oxygenates most commonly The MTBE market predominates in Europe and the US; however, its use has become restricted owing to its high solubility in water, as well as its toxic effect and degradation products, which have become the object of environmental concern [7,8].
Menezes,e M. In terms of octane rating, Brazilian gasoline is comparable to the American and European products. Gasolines containing high pro- portions of aromatic hydrocarbons such as benzene, toluene, xylenes, and olefins produce relatively high concentrations of reactive hydrocarbons [12,13].
Therefore, gasolines formulated with oxygenated compounds may contain lower amounts of aromatic compounds. Gasolines with high concentrations of aromatics have a greater tendency to emit unburned hydrocarbons, which are not easily oxidized in catalytic converters and are precursors of photochemical contamination .
- Ottoman Empire and Islamic Tradition (Phoenix Book).
- The Karoo: Ecological Patterns and Processes.
- Modernists at Odds: Reconsidering Joyce and Lawrence.
The most important pollutants associated with the operation of internal combustion engines are carbon monoxide, unburned or partially oxidized hydrocarbons, nitrogen oxides and particulate material. CO2, though traditionally not considered a pollutant, accumulates in the atmosphere, leading to climatic changes .
All oxyge- nated fuels reduce the emission of carbon monoxide CO and unburned hydrocarbons from automobile exhausts, in addition to being less photochemically reactive than most of the hydrocarbons of gasoline [16,17]. Based on studies involving vehicles, Reuter et al. Poulopoulos et al. They also detected a general decrease in the emission of aromatic hydrocarbons.
Al-Hasan  carried out a series of tests using mixtures of gasoline and ethanol, and found a reduction of approxi- mately In tests involving two-stroke engines using gasoline and ethanol mixtures, Roger Magnusson et al. Thus, the use of gasolines formulated with ethanol is an important factor in the reduction of environmental contamination. The vapor pressure of gasoline is a fundamental physicochemical property for the level of emission of volatile compounds in the gasoline supply system and in the combustion process, especially in starting the engine on cold days and in continuous operation on hot days.
Today there is a strong tendency for a reduction of the volatility parameters, among them the vapor pressure in gasoline. It was found that, for a gasoline with the same composition, a 0. Curiously, in older vehicles equipped R. A study in France  indicated that the best global correlation with drivability was given by the expression containing two variables, Reid vapor pressure and percent of evaporated compounds at 8C. These studies have confirmed that avehicles satisfactory performance depends on a minimal volatility of the fuel.
At high operating temperatures, the most common phenomena that affect the fuel systems in vehicles are vapor lock and percolation. The purpose of the investigation was to study the effects of high temperatures such as exist during the first stages of injection on the vapor pressures of several fuels and certain fuel mixtures, and the relation of these vapor pressures to the preparation of the fuel for combustion in high-speed fuel injection engines. The main purpose of this study was to identify prospective chemistry teachers' mental models of vapor pressure. The study involved 85 students in the Chemistry Teacher Training Department of a state university in Turkey.
Participants' mental models of vapor pressure were explored using a concept test that involved qualitative comparison tasks.
The Po of a semi-membrane tank must not exceed The Po of an integral tank must not exceed If the surfaces of an independent tank type B are The Po of a membrane tank must not exceed The hysteretic evapotranspiration - vapor pressure deficit relation. Diurnal hysteresis between evapotranspiration ET and vapor pressure deficit VPD was reported in many ecosystems but justification for its onset and magnitude remain incomplete with biotic and abiotic factors invoked as possible explanations.
To place these explanations within a mathematical framework, ';rate-dependent' hysteresis originating from a phase angle difference between periodic input and output time series is first considered. Lysimeter evaporation E measurements from wet bare soils and model calculations using the Penman equation demonstrate that the E-VPD hysteresis emerges without any biotic effects due to a phase angle difference or time lag between net radiation the main driver of E, and VPD.
The phase angle difference representation earlier employed was mathematically transformed into a storage problem and applied to the soil-plant system. The transformed system shows that soil moisture storage within the root zone can produce an ET-VPD hysteresis prototypical of those generated by phase-angle differences. To explore the interplay between all the lags in the soil-plant-atmosphere system and phase angle differences among forcing and response variables, a detailed soil-plant-atmosphere continuum SPAC model was developed and applied to a grassland ecosystem.
The soil moisture dry-down simulations also suggest that modeled root water potential and leaf water potential are both better indicators of the hysteresis magnitude than soil moisture, suggesting that plant water status is the main factor regulating the hysteretic relation between ET and VPD. Hence, the genesis and magnitude of the ET-VPD hysteresis are controlled directly by both biotic factors and abiotic factors such as time lag between radiation and VPD originating from boundary layer processes.
Controlling the vapor pressure of a mercury lamp. The invention described herein discloses a method and apparatus for controlling the Hg vapor pressure within a lamp. This is done by establishing and controlling two temperature zones within the lamp. One zone is colder than the other zone. The first zone is called the cold spot.
By controlling the temperature of the cold spot, the Hg vapor pressure within the lamp is controlled. Likewise, by controlling the Hg vapor pressure of the lamp, the intensity and linewidth of the radiation emitted from the lamp is controlled. Dosimeter for monitoring vapors and aerosols of organic compounds. A dosimeter is provided for collecting and detecting vapors and aerosols of organic compounds. The dosimeter comprises a lightweight, passive device that can be conveniently worn by a person as a badge or placed at a stationary location.
The dosimeter includes a sample collector comprising a porous web treated with a chemical for inducing molecular displacement and enhancing phosphorescence. Compounds are collected onto the web by molecular diffusion. The web also serves as the sample medium for detecting the compounds by a room temperature phosphorescence technique. The term Reid vapor pressure means the vapor pressure of a liquid at a This Standard is available at Laboratory procedures, calculations, and sample results are described for a freshman chemistry experiment in which the Clausius-Clapeyron equation is introduced as a means of describing the variation of vapor pressure with temperature and for determining enthalpy of vaporization.
Apparatus of the Vapor-pressure Measurements for Natural Refrigerants. An apparatus for measuring the vapor-pressures was newly designed and constructed in order to make the basic thermodynamic properties for environmentally acceptable refrigerants clear.
- Beginning Wing Chun.
- City Schools: Lessons from New York?
- The students elements of geology?
- Lemon Meringue Pie Murder (Hannah Swensen Mystery, Book 4).
With respect to the pressure measurement, two kinds of presure transducer were adopted. A quartz crystal pressure transducer was calibrated against the dead weight pressure gauge and barometer.
The vapor-pressures for R, Ra, R propane , Ra iso-butane and n-pentane were measured in the temperature range between As the results of vapor-pressure measurements, the reliability of the experimental apparatus as well as the reproducibility of the experimental data were confirmed. In addition, coefficients of Antoine vapor pressure equation were determined from the experimental data. Normal boiling points for environmentally acceptable refrigerants were also determined with high accuracy. This experiment, designed for a general chemistry laboratory, illustrates the use of Dalton's law of partial pressures to determine the vapor pressure of a volatile liquid.
A predetermined volume of air is injected into a calibrated tube filled with a liquid whose vapor pressure is to be measured. The volume of the liquid displaced is greater than…. Vapor pressure is a fundamental property of a pure substance. This property is the pressure of a compound 's vapor in thermodynamic equilibrium with its condensed phase solid or liquid. When phase equilibrium condition is met, phase coexistence of a pure substance involves a continuum interplay of vaporization or sublimation to gas and condensation back to their liquid or solid form, respectively.
Thermogravimetric analysis TGA techniques are based on mass loss determination and are well suited for the study of such phenomena. In this work, it is shown that TGA method using a reference substance is a suitable technique for vapor pressure determination. This method is easy and fast because it involves a series of isothermal segments.
In contrast to original Knudsen's approach, where the use of high vacuum is mandatory, adopting the proposed method a given experimental setup is calibrated under ambient pressure conditions. The theoretical framework of this method is based on a generalization of Langmuir equation of free evaporation: The real strength of the proposed method is the ability to determine the vapor pressure independently of the molecular mass of the vapor. A demonstration of this method has been performed using the Clausius-Clapeyron equation of state to derive the working equation.
This algorithm, however, is adaptive and admits the use of other equations of state. Vapor pressure determined in this study spans from few mPa up to several kPa.
Once the p versus T diagram is obtained, phase transition enthalpy can additionally be calculated from the data. Secondary drying is the final step of lyophilization before stoppering, during which water is desorbed from the product to yield the final moisture content. We studied how chamber pressure and partial pressure of water vapor during this step affected the time course of water content of aqueous solutions of polyvinylpyrrolidone PVP in glass vials.