The Aquatic Toxicity Section's properties are all either LC50 or EC50 values. LC50, the median lethal concentration, is the concentration of a chemical that will kill half of a test population in a given period of time. EC50, the half maximal effective concentration, refers to the concentration of a chemical that will produce a response equal to 50% of the maximum response for a given time of exposure.

The property control field contains a label and a values control. Each property field contains a label, a datum control, an estimated value control, and a units control.

1	Property Control: the property control displays the main property for which values are being displayed. The section's fields display values for each subproperty. For example, the above image is displaying a value of 3.67 kg/m3 for the LC50, Fathead Minnow aquatic toxicity.
2	Datum Control: displays the field's physical property's data value. A green triangle in the datum control's upper right corner indicates that additional data are available. (See below.)
3	Estimate Control: displays the field's physical property's estimated value.
4	Units Control: displays the current units for the field's physical property.

All the fields in this section contain numerical values. Thus, they all appear similar and are edited in the same manner.

The Property edit control at the top of the section (to the right of the "Property:" label) is used to specify to the current property being displayed in the section's property fields.

The Data column of each field displays a physical property data value. The data value is displayed in the units shown in the Units column.

Clicking the left mouse button on a datum control activates a datum edit dialog enabling you to enter a value, accuracy, units, reference and comment. See documentation on the Datum-Units-Reference Edit Dialog for details.)

A green triangle in the data control's upper right corner indicates that additional data are available. (See documentation on the Datum-Units-Reference All Data Dialog for details on managing data having different status.)

Clicking the right mouse button within a field's datum control activates the field's datum commands menu.

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

• Edit All Data: uses the All Data dialog to enable editing data having status values of passive, rejected or unknown. See Datum-Units-Reference All Data Dialog for documentation.)
• Edit Data: enables you to view and mofidy the current physical property's datum. The property value, accuracy, units of measure, reference and comments can be viewed and edited. See Datum-Units-Reference Edit Dialog for detailed documentation.

  Each property field runs a set of verification tests to check the validity of an entered value. Specifically, every toxicity value must be a number greater than or equal to 0.

  Cranium or Synapse will signal an error if the entered value fails a physical property verification test.

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 Chemicals Chapter. (See documentation on Navigation Overview for details on navigating chapters and pages.)
3. Scroll down to the Aquatic Toxicity Section and click the left mouse button in the property control field. The application activates the Aquatic Toxicity Properties dialog. Choose the 'LC50, Fathead Minnow' entry.
4. Click the left mouse button in the 96 Hrs data control. The application activates the property data entry dialog.
5. Enter a value for the property, the accuracy of the value, the units, a reference and one or more comments.
6. Press the Save button to store the values in the document and display the value in the field.

Each property field runs a set of verification tests to check the validity of the entered value. For example, the 96 Hour LC50, Fathead Minnow field checks that the entered value is greater than or equal to 0.0 mg/m3. The application signals an error if the entered value fails any of these verification tests.

The Estimates column of each field displays the physical property's estimated value. The value is displayed in the units shown in the Units column.

Clicking the left mouse button on an estimate control activates the Estimation Details dialog.

The Estimation Details dialog shows the estimated value, the technique used to generate the estimate, and any comments generated during the estimation. The dialog also has two buttons to provide more information about the technique used to generate the estimate:

• Tech Notes: displays the general notes associated with the estimation technique.
• Tech Ref: display the document associated with the technique's reference.

Clicking the right mouse button on the estimate control displays the command menu.

The menu's commands enable you to copy, cut and clear values from the estimate control. (You cannot paste a value into an estimate control.) See Common Menu Commands for documentation on the commands commonly found on command menus. Some of this field's more specific commands are:

• Compute Estimate: activates the Property Estimation dialog which enables you to estimate the current physical property. The functionality of this command is similar to that of the Commands menu Compute Estimates command. The key difference is that the estimates control's menu command limits the estimation to only the current physical property. See Estimating Chemical Properties for additional documentation.
• Select Technique: enables you to specify the estimation mode and the estimation technique used to estimate the current physical property. Selecting this command activates the Estimation Technique Information dialog.

  The dialog lists two estimation modes: Automatic and Manual. By default all estimations are initially set to Automatic Mode. Once you choose Manual Mode, the list of estimation techniques is enabled allowing you to choose any estimation technique known to the application. See documentation on Manual Techniques Dialog for details about manually selecting estimation techniques.
• Detail Estimate: activates the Details Dialog displaying information about the estimation technique used. See documentation on the Estimate-Units-Technique Dialog for details.

Selecting new units from the list and press 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. All estimated values are generated by Cranium and Synapse in standard units. (See documentation on the Property Units Dialog for additional details on changing property units.)

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 critical temperature, all documents will update their critical temperature displays using the newly selected units.

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.

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.