Phase Invariants Section
Applicability: Cranium, Synapse (core versions 0315+)

This section contains one large table displaying phase invariants such as azeotropes, eutectics, and consolute solution points.

Property Control: this control shows the property whose values are currently displayed in the section's table control.
Table Control: displays the selected physical property's values. A green triangle in the table control's upper right corner indicates that additional data are available. (See below.)

Note that the table control contains several additional controls enabling you to select units for the temperature and property values.

Temperature Units Control: this control shows the units in which temperature values are displayed.
Pressure Units Control: this control shows the units in which pressure values are displayed.
Composition Units Control: this control shows the units in which composition values are displayed.
Selecting a Physical Property

The Property Control and Type Control are located at the top of the section. The Property control is used to select the physical property whose values are to be displayed.

Clicking the left mouse button on either control activates the Properties dialog.

Editing Data Values

The section's table control displays the selected property's data values. Each phase invariant datum contains a temperature, pressure, and composition. The units for these values are shown in the units row near the top of the table. A green triangle in the upper right corner of the property data box indicates that additional data are available. (See documentation on the Phase Invariants All Data Dialog for details on managing data of different status.)

Clicking the left mouse button on the data values table control activates the Phase Invariants Edit Dialog enabling you to add, remove, and edit phase invariant data. (See here for documentation.)

Data Table Commands Menu

Clicking the right mouse button within the data table control displays the field's data commands menu.

The menu's commands enable you to copy, cut and paste values to and from the data table control. See Common Menu Commands for documentation on the commands commonly found on command menus. Some of this field's more specific commands are:

  • Edit All Data: uses the All Data dialog to enable editing data having status values of passive, rejected or unknown. See All Data Dialog for documentation.)
  • Edit Data: enables you to view, add, remove, and edit the currently selected phase invariant property's data values. enabling you to add, remove, and edit phase invariant data. See Data Edit Dialog for detailed documentation. (Clicking the left mouse button on the table control will also execute this command.)
Example: Enter maximum boiling azeotropic data

In this example we will enter the following values for the maximum boiling azeotrope of the cyclohexane (1) + 2-propanol (2) mixture.

Component 2 Temperature [K] Pressure [kPa] X,1 [molf]
2-Propanol 342.64 101.3 0.5887
Ethyl acetate 344.66 101.3 0.4784
Accuracies: temperature = 0.01 K; pressure = 0.1 kPa; compositon = 0.001.

  1. Open a "working" copy of the MKS Sample Knowledge Base document or create a copy of the document. See here for details on how to create copies of documents.
  2. Change to the Chemicals Chapter and navigate to cyclohexane. (See the Navigation Overview documentation for details on navigating chapters and pages.)
  3. Scroll down to the Phase Invariants of Binary Mixtures Section and click the left mouse button in the property control. The application activates the Phase Invariants properties dialog.
  4. Select 'Azeotrope, Minimum Boiling' from the list of properties.
  5. Press the OK button. The dialog will close and the application will display any current minimum boiling azeotrope data.
  6. Click the left mouse button anywhere in the large values area of the section's table control. The application activates the Property Data dialog.
  7. Click the left mouse button on an empty row in the dialog's table control. Press the Edit button. The application activates the Property Data Entry dialog. (The controls highlighted in yellow indicate required values.)
  8. Using the data table given above, enter values for 2-propanol. Enter a value for Component 2, the temperature, and the pressure. Select the units to match the units given in the data table. Also, enter the accuracies for each value as given in the comment below the data table.
  9. Note the data table gives a value for X,1, the mole fraction of cyclohexane. However, the dialog requires a value for X,2, the mole fraction of 2-propanol. To enter this value, press the dialog's Enter X,1 button. The Component 1 Composition Dialog is activated.

    Enter the composition of component 1, cyclohexane, and enter the composition accuracy as given in the data table above. Then press the dialog's OK button.

    The dialog will subtract the entered value from 1.0 and enter the result in the datum edit dialog.

  10. You would then normally enter values for the reference and comments. And finally press the dialog's OK button. The entered datum is added to the data edit dialog.
  11. Repeat the process for the ethyl acetate entry.
  12. Finally press the data edit dialog's Save button to store the phase invariant values into the current document.
Changing Units

The second header row of the section's data table control contains edit controls displaying the current units for temperature, pressure, and composition. Clicking the left mouse button within one of these units controls activates the Set Property Units dialog.

Selecting new units from the list and pressing the OK button changes the current units in which the property is displayed. (Note that all data are stored in their original units - changing the displayed units does not change any stored data.) The dialog's Std Units button displays the default units used by Cranium and Synapse for the current physical property. (See documentation on the Property Units Dialog for additional details on changing property units.)

Tip: All displayed units change

The units set via the Set Property Units dialog, accessed either from the Options menu's Set Units command or clicking on the Units control in a physical property field, are assigned for all documents in the application. For example, if you have three knowledge base documents open and then change the units of the vapor pressure, all documents will update their vapor pressure displays using the newly selected units.

Also note that changing temperature or pressure units will change these values for all values throughout the application. Thus, changing the temperature units in this section's table control will change the temperature units in the Temperature-Pressure Dependent Section as well as the temperature dependent sections in the mixture chapter.

Units are also stored in the application. The next time Cranium or Synapse starts, the set of units used in your last session will be used again.

Tip: Units Error

Sometimes, when working with properties that have a composition variable, the application will display the term '- units err -' instead of the composition value. This is because either a chemical is missing from the knowledge base or the chemical's molecular weight is not known. See documentation on Units Error for details.

Related Documentation
Topic Description
Estimating Chemical Properties a short video demonstrating how to estimate physical properties using either Synapse or Cranium.
Getting Started using Cranium provides a quick tour of Cranium's capabilities including a discussion of physical property estimation and structure editing.
Chemicals Chapter the chemicals chapter contains numerous sections for entering and displaying data and estimates including the chemical structure section.