Percent by volume

Percent by volume is the most common unit of concentration used for mixtures of gases. 

It is also true that the percent by relative numbers of molecules in a mixture of gases has the same value as the percent by volume of those gases. Therefore, when we say that the atmosphere is 78 percent by volume, we mean that in a sample of 100 liters of air we 

Because concentrations as relative numbers of particles are so common in mixtures of gases, related units are the following  

we could also describe the concentration of in the atmosphere as 780 thousand parts per million. It is more common, however, to use ppm for gases that are present in very small quantities. For example, the concentration of carbon monoxide (CO) in a polluted atmosphere might be 10-20 ppm, or 10-20 molecules of CO for every million air molecules total. 

The molarity of a solution (symbolized M) is defined as the number of moles of solute present per liter of total solution. For example, if 2.00 moles of table salt are dissolved in enough water to make one liter of solution, then the molarity of the solution is 2.00 M, pronounced 2.00 molar. Molarity is probably the most common tmit of concentration used in chemistry, especially when working with aqueous solutions. 

This is a variation of the above which is usually used for a solution of a liquid in a liquid. It is often used for expressing the concentration of alcoholic drinks. 

Here the volume of the solute is included in the total volume. So a 1 dm bottle of table wine which is 12.5% ethanol contains 125 cm of alcohol and 875 cm of water. A 500 ml can of beer, which is 4.5% alcohol, contains 22.5 cm of ethanol and 477.5 cm of water. This simple example does not take into account the slight shrinkage in volume you get on mixing alcohol and water. 

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The autoignition temperature is the minimum temperature required for self-sustained combustion in the absence of an external ignition source. The value depends on specified test conditions. Tht flammable (explosive) limits specify the range of concentration of the vapor in air (in percent by volume) for which a flame can propagate. Below the lower flammable limit, the gas mixture is too lean to burn above the flammable limit, the mixture is too rich. Additional compounds can be found in National Fire Protection Association, National Fire Protection Handbook, 14th ed., 1991. 

Substance Autoignition temperature, °C Flammable (explosive) limits, percent by volume of fuel (25°C, 760 mm) ... 

The upper and lower flammabihty limits are the boundary-line mixtures of vapor or gas with air, which, if ignited, will just propagate flame and are given in terms of percent by volume of gas or vapor in the air. Each of these limits also has a temperature at ch the flammabihty limits are reached. The temperature corresponding to the lower-hmit partial vapor pressure should equal the flash point. The... 

Example 6 Solvent Rate for Absorption Let us consider the absorption of acetone from air at atmospheric pressure into a stream of pure water fed to the top of a packed absorber at 25 C. The inlet gas at 35 C contains 2 percent by volume of acetone and is 70 percent saturated with water vapor (4 percent H2O by volume). The mole-fraction acetone in the exit gas is to be reduced to 1/400 of the inlet value, or 50 ppmv. For 100 kmol of feed-gas mixture, how many Idlomoles of fresh water should be fed to provide a positive-driving force throughout the pacldug How many transfer units will be needed according to the classical adiabatic method What is the estimated height of pacldug required if Hqq = 0.70 m ... 

Another phenomenon is the increase in power required with percent sohds, which makes a dramatic change at approximately 40 percent by volume, and then dramatically changes again as we approach the ultimate weight percent of settled solids. This phenomenon is covered by Oldshue (op. cit.), who describes conditions required for mixing slurries in the 80 to 100 percent range of the ultimate weight percent of settled sohds. 

These reactors for hquids and liquids plus gases employ small particles in the range of 0.05 to 1.0 mm (0.0020 to 0.039 in), the minimum size hmited by filterability. Small diameters are used to provide as large an interface as possible since the internal surface of porous pellets is poorly accessible to the hquid phase. Solids concentrations up to 10 percent by volume can be handled. In hydrogenation of oils with Ni catalyst, however, the sohds content is about 0.5 percent, and in the manufacture of hydroxylamine phosphate with Pd-C it is 0.05 percent. Fischer-Tropsch slurry reac tors have been tested with concentrations of 10 to 950 g catalyst/L (0.624 to 59.3 IbiTi/fF) (Satterfield and Huff, Chem. Eng. Sci., 35, 195 [1980]). 

Ethanol fermentation is a particularly good example of product accumulation inhibiting the microbial culture. Most strains of yeast have a much slower alcohol production rate when ethanol reaches about ten percent, and the wine or said strains that achieve over 20 percent by volume of ethanol are very, very slow. A system known as the Vacuferm for removal of alcohol by distillation as it is formed is... 

Flash Point and Flammable Limits Flash points and flammable hmits in percent by volume have been tabulated by the National Fire Protection Association (NFPA) (National Fire Protection Association, Fire Hazard Properties of Flammable Liquids, Gases, and... 

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 ... 

Various types of rapid, adiabatic compressions have caused explosions. With propane at an initial temperature of 25°C, To = 432°K (I59°C) for compression and specific heat ratios of 25 and I.I3, respectively. Assume that now air enters a compressor to bring propane into the flammable range at 5 percent by volume. The mixture then will be mostly air with k = 1.47. The same compression ratio of 25 will elevate the final temperature T2 to 834°K (56I°C), i.e., above the published autoignition temperature of 450°C for propane and perhaps high enough to cause an explosion. 

FIG. 26-31 Estimated maximum downwind distance to lower flammable limit L, percent by volume at ground level in centerline of vapor cloud, vs. continuous dense vapor release rate at ground level. E atmospheric stability. Level terrain. Momentary concentrations for L. Moles are gram moles u is wind speed. (From Bodmtha, 1980, p. 105, by permission.)... 

Explosive limits are expressed in percent by volume of vapor in air. LELs and UELs have been determined in fire and safety, and health laboratories for all substances likely to be found in industry. Typical values for some solvents and gases are given in Table 3. 

Flammable Limits in Air - This is a concentration expressed as percent by volume of the chemical in air, whereby spontaneous combustion will be supported. The lowest concentration where combustion will be supported is known as the lower flammability limit (LFL) or lower explosion limit (LEL). LEL and LFL are considered interchangeable. The upper concentration limit is the UFL (Upper Flammability Limit) or UEL (Upper Explosion Limit). 

The main advantage of absorption is its applicability to the control of pollutant gases present in large concentrations (several percent by volume). In these applications, removal efficiencies of 98°/ or greater can be achieved. The main disadvantage is inflexibility to achieve the best performance, the gas stream components are fixed once the column is designed, (see Table 13.1.3)... 

Carbon monoxide (CO) is a colurless, odorless, and tasteless gas. Inhalation of as little as 0.3 percent by volume can cause death within thirty minutes. The exhaust gas from spark ignition engines at an idle speed has a high CO content. For this reason NEVER allow an engine to run in an enclosed space such as a closed garage. 

Sand content of the mud is reported in percent by volume. Also reported is the point of sampling, e.g., flowline, shaker, suction, pit, etc. Also, solids other than sand may be retained on the screen (lost circulation material, for example) and the presence of such solids should be noted. 

To determine the O/W ratio, it is first necessary to measure oil and water percent by volume in the mud by retort analysis. From the data obtained the oil/water ratio is calculated as follows ... 

Fig. 11-6 Concentrations of gases in the smoke from an experimental fire of Trachypogon grass from Venezuela as a function of time and the stack gas temperature. The dotted line separates the flaming phase from the smoldering phase. Concentrations are in percent by volume for CO2, in volume mixing ratios (ppm) for the other species (1% = 10000 ppm). (Used with permission from Crutzen and Andreae (1990). Science 250 1669-1678, AAAS.)...

Average treatment volume was 600 gallons. All fluids contained 1% (by volume) of water wetting non-emulsifier. The treatments utilizing a cationic organic polymer included the polymer in all aqueous based fluids. The reported polymer concentration of one percent by volume of the aqueous polymer solution as supplied. Active polymer concentration is actually less than this. When the clay stabilization polymer was part of the well treatment, a non-ionic water wetting nonemulsifier was used. 

A corrosion inhibitor was present in all acid fluids. Eight of the well treatments incorporated a cationic organic polymer mineral fines stabilizer in the first three treatment stages. The active polymer concentration was less than the reported aqueous polymer concentration of one percent (by volume). Again, this was because the polymer was not supplied as a 100% active product. 

Percentages can be used as factors. The percentage of something is the number of parts of that thing per hundred parts total. Whatever unit(s) is used for the item in question is also used for the total. For example, the percent by mass of water in a solution is the number of grams of water per hundred grams of solution or the number of kilograms of water per 100 kg of solution. The percent by volume of alcohol in a mixed drink is the number of milliliters of alcohol in lOOmL of the drink, and so forth. If the words by volume or some other similar words are not stated, assume percent by mass. 

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