Typically you first enter state variable values and then request Cranium or Synapse to generate an estimated property value. Sometimes, the opposite process is desired - you specify a desired property value and ask the application to estimate the state variable values that would generate that estimate.

For example, the estimated entropy values shown below are all equal to 1000 J/kg K. Each entropy value was entered as a goal value with an input pressure starting at 100 kPa and being incremented by 20 kPa. The temperature was then varied until the goal value was matched.

The Goal Seek dialog has controls for entering an initial temperature or pressure value, a goal value, and for performing the goal seek operation.

1	Temperature Control: enables you to enter a value for the temperature that will be used as either a fixed value or an initial guess.
2	Pressure Control: enables you to enter a value for the pressure that will be used as either a fixed value or an initial guess.
4	Independent Variable Control: enables you to select either temperature or pressure as the independent variable, i.e., the variable that will be varied to achieve the goal value.
2	Property Control: displays the property being estimated.
3	Goal Control: enables you to enter your goal physical property value.
4	Value Control: displays the value estimated given the current temperature and pressure. This value should start approaching the goal value as the solution process proceeds.
5	Delta Control: displays the difference between the goal value and the current estimated value. This value should approach zero as the solution process proceeds.
6	Start Seek Button: pressing this button starts the solution process.

1. Open the MKS Sample Knowledge Base document. (Open a "working" copy or create a copy of the document (see here) if you are just experimenting with this functionality.)
2. Make sure the current units are: C for temperature, kPa for pressure, and J/kg K for the vapor entropy. (See documentation on the Property Units Dialog for details on changing units.)
3. Change to the Chemicals Chapter and navigate to '1,1,1,2-Tetrafluoroethane'. (See the Navigation Overview documentation for details on navigating chapters and pages.)
4. Scroll down to the Temperature and Pressure Dependent Section and click the left mouse button on the property control. (See the section's documentation for additional details.)
5. The Properties Dialog is activated. Select 'Entropy, Vapor - f(T,P)' as the property and 'Estimates' as the values type.
6. Now click the left mouse button on the Section's large table control. The application activates the Estimates dialog. (See documentation on the Temperature and Pressure Dependent Estimates Dialog for additional information.
7. Click the left mouse button on the dialog table's first row and press the Goal Seek button. The application activates the Goal Seek Dialog.
8. Enter a temperature guess of 50 C, a pressure value of 100 kPa, and a goal value of 1200 J/kg K.
9. Press the dialog's Start Seek button. Pressing the Start Seek button begins the solution process. During the process, the application will update the temperature, estimate the property value, and compute the difference between this estimate and the goal value. For example, after the first iteration the temperature will have changed and the Goal Value controls will have been updated.
10. After the second iteration, the estimated value will be closer to the goal value.
11. Finally the iterations will converge onto a solution.
12. Pressing the Goal Seek Dialog's OK button will store the temperature, pressure and estimated value into the Estimates dialog.
13. Pressing the Estimates dialog's Save button will store this estimated value into the current document.

It is sometimes necessary to have a very good initial guess in order to find a successful goal seek solution. One way you can often get a good initial is by estimating some values at temperature values near those you expect for goal value.

You can use these estimated values as your initial guess by simply selecting them in the Estimates Dialog and pressing the Goal Seek button. The selected temperature will be assign to the Goal Seek dialog's controls.

Topic	Description
Getting Started using Synapse	provides a quick tour of Synapse's capabilities including examples of chemical product design.
Getting Started using Cranium	provides a quick tour of Cranium's capabilities including a discussion of structure editing.
Estimating Chemical Properties	a short video demonstrating how to estimate the physical properties of chemicals using either Synapse or Cranium.
Estimating Mixture Properties	a short video demonstrating how to estimate the physical properties of mixtures using either Synapse or Cranium.