Many mixture estimation techniques use binary interaction parameters. Typically, these parameters capture the interaction between two chemicals in the mixture. This section contains one large field, the Binary Interaction Parameters field, for managing these parameters. Very often interaction parameters come in pairs. The first parameter represents the i-j interaction. The second parameter represents the j-i interaction. Each parameter set contains a key string that enables you to differentiate between multiple types of interactions.

1	The key string enables you to enter several types of interactions.

Clicking the left mouse button on the section's table control activates the Binary Interaction Parameters Edit dialog. See documentation on the Binary Interaction Parameters Data Dialog for details.

Clicking the right mouse button within the 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 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 binary interaction parameters having status values of passive, rejected or unknown. See Edit All Data Dialog for documentation.)
• Edit Data: enables you to view and modify the current binary interaction parameters' components, key, value, reference, and comments. See Edit Data Dialog for documentation. (Clicking the left mouse button on the table control will also execute this command.)

Very often different references will often report different values for the same binary interaction parameter, i.e., parameters for the same components. The All Data dialog enables you to select which sets of parameters will be the active values used in generating estimates.

1. Open a knowledge base document. (Open a "working" document or create a copy of a document (see here) if you are just experimenting with this functionality.)
2. Change to the Techniques chapter, create a new technique to practice on, and scroll down to the Binary Interaction Parameters section.
3. Click on the Binary Interaction Parameters field’s table control. The application activates the Edit Binary Interaction Parameters dialog.
4. Select an empty row and press the dialog’s Edit button. Cranium activates the Parameter set edit dialog.
5. Press the dialog’s List button located to the right of the Comp 1 edit control. Cranium displays the Chemicals selection dialog.
6. Choose a chemical from the list.
7. Press the dialog’s List button located to the right of the Comp 2 edit control. Cranium displays the Chemicals selection dialog.
8. Choose a different chemical from the list.
9. Add a text string to the Key edit control. Typically this text string is of the form aij or a12 to differentiate the interaction between components i and j from the interaction between components j and i.
10. Enter a number for the value, the optional Source Information and press the dialog’s OK button. Cranium adds the parameter values to the Parameter Sets dialog.
11. Now add the parameter for the opposite interaction. This is the same procedure except that instead of entering "a12" for the key string, you would enter "a21".
12. Finally press the Parameters sets edit dialog’s Save button to store the parameters in the current document and display their values in the Binary Interaction Parameters field.

The two most common patterns for organizing interaction parameters are to enter them in an alternating pattern without a key:

Comp 1	Comp 2	Key	Value
1,4-Dioxane	1-Hexene		0.3577
1-Hexene	1,4-Dioxane		0.3755

or to enter them multiple times in the same order (typically alphabetical order) and use the key string to indicate which interaction is being represented:

Comp 1	Comp 2	Key	Value
1,4-Dioxane	1-Hexene	a12	0.3577
1,4-Dioxane	1-Hexene	a21	0.3755

Model code can be written for either pattern. However, we have found that the second pattern, using the key string to differentiate between types of parameters, to be clearer and more easily extended to techniques that have more than just two types of interaction parameters.

Topic	Description
Estimating Chemical Properties	a short video demonstrating how to estimate physical properties using either Synapse or Cranium.
Estimating Mixture 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 structure editing.
Techniques Chapter	the techniques chapter contains numerous sections for entering and displaying the code and parameter values needed to generate physical property estimates.