Liquids mixtures, flash point determination

Liquid Mixtures Flash point temperatures for mixtures of liquids can be estimated if only one component is flammable and the flash point temperature of the flammable component is known. In this case the flash point temperature is estimated by determining the temperature at which the vapor pressure of the flammable component in the mixture is equal to the pure component vapor pressure at its flash point. Estimation of flash point temperatures for mixtures of several flammable components can be done by a similar procedure, but it is recommended that the flash point temperature be measured experimentally. 

The flash point is the lowest temperature in degrees Centigrade at which so much vapor develops under normal pressure that it results in a flarmnable mixture together with the air over the liquid level. Different methods are used in the test with Cleveland cup being the most suitable method for testing additives. Cleveland open cup is used to determine flash and fire points of liquids with flash point above 79°C and below 400°C, such as additives... 

Flash point is the lowest temperature, corrected to normal atmospheric pressure (101.3 kPa), at which the application of an ignition somce causes the vapors of a specimen to ignite under the specific conditions of the test. Flash point determination methods are designed to be applied to a pure liquid but, in practice, mixtures are also evaluated. It is important to imderstand limitations of such data. The flash point of a solvent mixture can... 

The equilibrium vapor pressure above a confined liquid depends only on temperature. The fraction of the total pressure exerted by vapor pressure determines the composition of the vapor-air mixture. Thus when the total pressure is reduced, for example at high elevations or in vacuum tmcks, the vapor concentration in air increases. Since flash points are reported at a... 

The flash point represents the minimum temperature at whieh an ignitable mixture exists above a liquid surfaee. By definition, flash points are inapplieable to gases. Some solids, e.g. naphtlialene and eamphor, are easily volatilized on heating so that flammable mixtures develop above the solid surfaee and henee flash points ean be determined. (However, although these substanees ean be ignited, they generally need to be heated above their flash points in order for eombustion to be sustained this is the fire point .)... 

The lowest temperature of a flammable liquid at which it gives off sufficient vapor to form an ignitable mixture with the air near the surface of the liquid or within the vessel used. The flash point has been commonly determined by the open cup or closed cup method but recent research has yielded higher and lower flash points dependent on the surface area of the ignition source. Because of this aspect ASTM and other standard test methods have been recently withdrawn. They are under review until an adequate determination of a practical and comprehensive standard is composed and agreed upon. 

Flash Point (flash p). This is the lowest temperature at which a liquid will give off enough flammable vapor at or near its surface such that in intimate mixture with air and a spark or flame it ignites. The flash point of liquids is usually determined by the Standard Method of Test for Flash Point with the Tag Closed Cup Tester (ASTM D56-52, available from the American Society for Testing Materials, 1916 Race St, Philadelphia, Pa). This method is also the standard of the American Standards Association (ASA Z 11.24-1952, available from the American Standards Association, 70 East 45th St, New York, NY). The Interstate Commerce Commission uses the Tag Open Cup (TOC) Tester giving results 5—10°F higher (less flammable). Other methods frequently used are... 

The flash-point of a liquid mixture can be estimated by determining the temperature at which the equilibrium concentration of the flammable vapors in the air reach a concentration such that ( i/LFLi) = 1.0 where yi is the vapor phase mole percent of component i and LFL( is the lower flammability limit concentration of component... 

BUBBLE-POINT AND DEW-POINT CALCULATION. Determination of the bubble point (initial boiling point of a liquid mixture) or the dew point (initial condensation temperature) is required for a flash-distillation calculation and for each stage of a multicomponent distillation. The basic equations are, for the bubble point,... 

For a liquid that is a mixture of compounds that have different volatility and flash points, its flash point shall be detemined as specified above on the material in the form in which it is to be shipped. If it is determined by this test that the flash point is higher than 20°F (-6.67°C) a second test shall be made on a sample of the liquid evaporated from an open beaker (or similar container), under ambient pressure and temperature (20° to 25°C) conditions, to 90 percent of its original volume or for a period of 4 hours, whichever comes first. The lower flash point of the two tests shall be the flash point of the material. 

Flash Point — The lowest temperature, as determined by standard tests, at which a liquid emits vapor in sufficient concentration to form an ignitable mixture with air near the surface of the liquid in a test vessel. Note that many of these common chemicals have flash points below room temperature. 

Combustible liquid flash point (closed cup) 85.5°C (186°F) the vapor forms explosive mixtures with air, the explosive range not determined. 

Plastic Solvent n.o.s. A name commonly used for mixtures of liquids employed for dissolving plastics or for thinning plastic cements. In general, they may contain flammable liquids, such as acetone, amyl acetate, or some of the alcohols or ketones. The classification is determined by the flash point. ICAO A2... 

The sustained burning test was originally developed for British Standard BS-3900 and adapted by ASTM. The purpose of the test is to determine the sustained burning characteristics of solvents by direct experiment rather than by deducing characteristics from flash point data. Mixtures of some flammable liquids (e.g., alcohol and water) are classified as flammable based on the closed-cup flash point method. Some mixtures may be classed as flammable even though they do not sustain burning. The test is performed in a block of aluminum with a concave depression called a well. The liquid under test is heated to a temperature of 49 C and a flame is passed over the well and held in position for 15 s. The specimen is observed to determine if it can sustain burning. 

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