One of Cranium’s and Synapse's key capabilities is to estimate physical properties quickly, easily and accurately. To estimate a property the application first collects all applicable techniques, sorts them by accuracy, and then tries each one until an estimate is generated.

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. Using the tabs at the top of the document, change to the Mixtures Chapter by clicking the left mouse button on Mixtures tab. (See the Navigation Overview documentation for details on navigating chapters and pages.)
3. Create a new Mixture entity by pressing the "+" button in the menubar or executing the "Add New Page" command found on the Edit menu. A new, blank Mixture page will be added to the current document.
4. Now click the left mouse button on the Component Section's large table control. The application will activate the Mixture's Components edit dialog. (See documentation on the Mixture Components Dialog for details.)
5. Click the left mouse button on the first row and press the dialog's Edit button. The application will activate the Component Edit dialog. (You can also double-click on a table's row to activate the edit dialog.)
6. Enter "Ammonia" into the Component Chemical control and, optionally, an entry into the Comments control. Finally, press the dialog's OK button.
7. Now double-click the left mouse button on the table's second row. The application will again activate the Component Edit dialog.
8. Enter "Argon" into the Component Chemical control and, optionally, an entry into the Comments control. Finally, press the dialog's OK button.
9. Finally, press the Components Edit dialog's Save button to store the entered components into the current document.
10. Click the left mouse button in the Identifier Pane, the large white box at the top of the page. The application will activate the pane's datum edit dialog.
11. Press the dialog's Recommend button. The application will retrieve the entered mixture components and append their names together, with a "+" separator, to form the mixture's recommended name.
12. Press the Identifier edit dialog's Save button to store the entered identifier into the current document.

This example is a continuation of the previous example so please first complete those steps.

1. Scroll to the Composition/Temperature Dependent Section. Click the left mouse button on the section's Property control. The application will activate the Properties dialog.

   1	The Properties control displays all properties that are functions of both composition and temperature.
   2	The Values Type control shows the types of values that can be displayed in the field's table.

2. Select "Viscosity, Vapor - f(T,X)" from the Properties control and "Estimates" from the Values Type control. Then press the dialog's OK button.
3. Next click the left mouse button in the section's large table control. The application will activate the data edit dialog.
4. Click and hold down the left mouse button on the table's first row. Then, while continuing to hold the button down, drag the mouse beyond the bottom of the table. The table will automatically scroll, selecting rows as it does. Once the table reaches its last row, release the mouse button.
5. Press the dialog's Series button and select Composition Series from the displayed menu. The application will activate the Composition Series dialog. (Note that the compositions of only two components can be changed when a series is being generated. The dialog's Compositions section enables you to specify these two compositions, the one whose composition varies and the one whose composition is the remainder, and the fixed composition value for all other components.)

   1	The component whose composition will be varied to generate the series.
   2	The component whose composition will be calculated as the remainder after all other component compositions are totaled.
   3	The constant temperature that will be used for each series entry.
   4	The starting value for the variable composition.
   5	The ending value or increment used to calculate the series of compositions.

6. Select "Variable" for ammonia's composition, "Remainder" for argon's composition, 34.85 C for the temperature, 0.0 mol frac for the starting composition and 1.0 for the ending composition. If your application is using other units, please convert the values given here or change the current units. (See documentation on the Properties Units Dialog for details on setting units.)
7. The application will use the series dialog's values to generate state variables for the current property.

   1	State variables generated by the Composition Series dialog.

8. Run the Compute Estimates command from the Commands menu.
   The application displays the Property Estimation Dialog.
9. Press the dialog's Start button. The application estimates each property documenting its progress in the dialog.
10. Once all estimates have been generated, expand the Viscosity, Vapor node, by clicking on the 'plus' sign to the left of the property, and continue to expand all child nodes. The display should appear similar to the following.
    This image shows that the knowledge base used the 'Visc,v (T,X): Wilke Equation [MKS]' technique.
11. Press the Property Estimation dialog’s Save button. The application stores the estimates in the current knowledge base and displays them on the current mixture's page.
12. The agreement between estimated values, green diamonds, and data values, blue squares, is good.

Cranium and Synapse store estimation techniques as entities just like chemicals, mixtures and references. Estimation techniques are stored in the Techniques Chapter of knowledge bases. (For details see documentation on the Techniques Chapter and Knowledge Base Documents.)

Every estimation technique contains two types of code: 1) accuracy/applicability code; 2) model code. When executed, the accuracy/applicability code returns two values: 1) a boolean true/false value indicating if the technique is applicable; 2) a numerical value denoting the technique's accuracy.

Often, for estimation techniques applicable to mixtures, the accuracy/applicability code will check for the presence of specific component chemicals. For example, several mixture techniques are not applicable if the mixture contains water. The accuracy/applicability code for these techniques usually contains the following lines:

The above code checks if one of the mixture's components is water. If it is, then the code return FALSE indicating that the technique is not applicable.

This example accuracy/applicability code shows how Cranium and Synapse decide which estimation technique should be used to estimate a particular property, of a particular chemical or mixture at a particular temperature, pressure and composition.

Before Cranium and Synapse perform an estimation, they first collect all estimation techniques for the property and execute each technique's accuracy/applicability code. Techniques whose codes return "false" are removed from consideration - those techniques are not applicable. The numerical result of each code represents the technique's accuracy. Techniques are sorted by this accuracy and the most accurate code is tried first. If this most accurate technique fails to generate and estimate, due to a missing parameter for example, the second most accurate technique is tried and so on.

Very often, Cranium and Synapse will need to estimate a dependent property during an estimation. For example, many mixture estimation techniques require physical property values of their component chemicals. Cranium and Synapse will use the same technique selection procedure described previously in a recursive manner, selecting the best estimation technique for the property of each component chemical.

For additional documentation on estimation techniques see Estimate Mixture Properties Dialog and Techniques Chapter.

Cranium and Synapse will automatically select the best applicable estimation technique. At times you may wish to manually specify which technique should be used for a particular property.

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 Mixtures Chapter by clicking the left mouse button on Mixtures tab. (See the Navigation Overview documentation for details on navigating chapters and pages.)
3. Using the Navigation menu's Go To command, change to the page displaying values for the "1,4-Dioxane + n-Butane" mixture.
4. Scroll down to the Composition Dependent Section and click on the the section's Property control. The application will activates the Properties dialog.
5. Select "Critical Temperature - f(X)" from the dialog's Properties control and "Estimates" from the Values Type control. (The Component control is disabled for this property.)
6. Click the right mouse button on the critical temperature field's estimates table control. The application displays the control's command menu.
7. Choose the Select Technique command from the menu. The application displays the Estimation Technique Information dialog. The property’s estimation mode is currently set to Automatic Mode. In Automatic Mode, Cranium and Synapse select the best applicable technique.
8. Change the Estimation Mode to Manual Mode and select the Tc(X): Li Technique [MKS]. (Note: the actual techniques available may differ depending upon the knowledge base you are using. The key concept for this example, is that you are able to choose a different technique than the one the application automatically selects.)
9. Press the dialog's OK button. The application will now use the Li's technique the next time it estimates the critical temperature.

Your selected manual techniques are stored within the current knowledge base. Thus, you may have two open knowledge bases that estimate the critical temperature by two different techniques. To check which techniques have been manually set, change to the Techniques chapter and run the Specify Manual Techniques command. (See documentation on the Set Manual Techniques Dialog for details.)

The Command Menu's Estimate Multiple Mixtures command enables you to estimate a property for several mixtures at a time.

For temperature, pressure and composition dependent properties, the dialog enables you to enter values for these state variables. Once these values are entered and one or more mixtures selected, pressing the dialog's Start button will generate estimates.

See documentation for the Estimate Multiple Mixtures Dialog for more details.

A mixture design is often done on a limited set of physical property constraints. For example, in the design of a new refrigerant mixture, we might design for constraints on bubble points, dew points, heat capacities and various thermodynamic derivatives. Once candidates have been designed, you can use the multiple mixture estimation capability to generate other properties, e.g., thermal conductivity, for each candidate at a series of temperatures for further evaluation.

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 structure editing.
Chemicals Chapter	the chemicals chapter contains numerous sections for entering and displaying data and estimates including the chemical structure section.