DePriester Charts provide an efficient method to find the vapor-liquid equilibrium ratios for different substances at different conditions of pressure and temperature. The original chart was put forth by C.L. DePriester in an article in '' Chemical Engineering Progress'' in 1953. These

nomogram A nomogram (from Greek , "law" and , "line"), also called a nomograph, alignment chart, or abac, is a graphical calculating device, a two-dimensional diagram designed to allow the approximate graphical computation of a mathematical function ...

s have two vertical coordinates, one for

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...

, and another for

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer. Thermometers are calibrated in various Conversion of units of temperature, temp ...

. "K" values, representing the tendency of a given chemical species to partition itself preferentially between liquid and vapor phases, are plotted in between. Many DePriester charts have been printed for simple hydrocarbons.

Example

For example, to find the K value of

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Ea ...

at 100 psia and 60 °F. # On the left-hand vertical axis, locate and mark the point containing the pressure ''100 psia.'' # On the right-hand vertical axis, locate and mark the point containing the temperature ''60°F.'' # Connect the points with a straight line. # Note where the line crosses the methane axis. Read this K-value off the chart (approximately 21.3).

References

{{reflist * * * * Chemistry Chemical engineering