Assay Distillation Curve

Distillation curve data corresponding to the laboratory distillation type and basis selected in the Stream Assay Definition Window are supplied in the table provided. The fitting procedure selected in the Assay Characterization Options Window is then used to process this distillation data.

Usage

To supply the distillation data, enter the percents distilled and corresponding temperatures. The percents must be on the basis chosen for the distillation data - either liquid volume or weight. The temperature unit may be changed by using the Unit-Of-Measure Selection Window which is displayed when the UOM button on the Toolbar is pushed. To add or delete rows from the table, use the Cut and Insert buttons. See Editing Tabular Data for additional information.

Additional Information

At least two distillation points must be given when the cubic spline or the alternate cubic spline (default) fitting method is used to develop the distillation curve. PRO/II uses a probability density function to fill in the curve when exactly two points are available. When the quadratic fitting method is used, a minimum of three distillation points are required for TBP curves and five points for the other types of curves. See Assay Characterization Options for more details.

It is always best to supply as many distillation points as possible for any assay. Furthermore, it is best if the distillation points cover or nearly cover the entire range for the curve.

PRO/II has methods for interpolation and extrapolation to provide missing data; however, it is always best to perform your own extrapolations based on your knowledge of the material.

Heavy refining stocks may be extrapolated with arithmetic probability paper to the following approximate end points: