Common Symbols Used in Gas and Liquid

Common Symbols Used in Gas and Liquid Chromatographic Schematic Diagrams... 

The mol fraction is dimensionless aU the mol fractions in any mixture sum to 1.00. The mol fraction of i is equivalent to the fraction of the molecules (or atoms) in the mixture that are of species i. This is the most widely used concentration unit in equilibrium calculations. By common convention the mol fraction of i in solids and liquids is given the symbol x while that in the gas phase is given the symbol y,. 

The arrangement of this table has much in common with that of Appendix B. See the description there for the reaction considered, and a list of the symbols used to indicate the experimental method. In the second column, gas, liquid, and solid have their usual meaning. Solutions are indicated by the name of the solvent appearing in the second column. As in Appendix B, in the first three and last three columns only a blank space means the entry above is to be carried down. In the other columns a blank space means the information is not known to us. 

A common symbol for volume percent is % (v/v). Commercial rubbing alcohol, for example, is an aqueous solution of isopropyl alcohol (a three-carbon alcohol) that contains 70 volumes of isopropyl alcohol per 100. volumes of solution, and the label indicates this as 70% (v/v). Parts-by-volume concentrations are most often used for liquids and gases. Minor atmospheric components occur in parts per million by volume (ppmv). For example, there are about 0.05 ppmv of the toxic gas carbon monoxide (CO) in clean air, 1000 times as much (about 50 ppmv of CO) in air over urban traffic, and 10,000 times as much (about 500 ppmv of CO) in cigarette smoke. 

The SI unit for volume concentration is mol/m. We will reserve the symbol Ci for the volume concentration expressed in mol/m. We will use the symbol for the volume concentration in the more commonly used unit, mol/L = mol/dm, called the molar concentration or the molarity. Volume concentrations are satisfactory for describing the composition of liquid or solid mixtures because the volume is comparatively insensitive to changes in temperature and pressure. Since the volume of a gas depends markedly on temperature and pressure, volume concentrations are not usually convenient for describing the composition of gas mixtures. 

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