Reaction Editor

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Navigation: User Guide ➔ Editors and Utilities ➔ Reaction Editor

Overview Reaction Block Data Section RB Sub Model (Model Theory)
Reaction Editor Reaction Block Summary Reaction Block Tabs (Main) Individual Reactions Reaction Extents Source / Sink /
Heat Exchange
Solving Order -
Sequential or Simultaneous
Energy Balance Heat of Reaction
/ Heat of Dilution
/ Partial Pressures

Related Links: Reaction File (RCT) Text Format


With all the features it provides, the SysCAD Reaction Editor makes it easier to create and edit reaction files. Therefore, we highly recommend our SysCAD users install it.

It is available with the latest install version of SysCAD, or from the Download section of our website (

Video Links

These short video clips are available in the Tutorial Section of the Help documentation, or directly in YouTube.

Set up the Reaction Editor

Installing the SysCAD Reaction Editor

  1. When SysCAD is installed there is an option to install the Reaction Editor. If this option was selected then there is nothing more to do.
  2. If Reaction Editor wasn't installed as part of the SysCAD install then the user needs to obtain a copy of the Reaction Editor installation file. They can obtain this:
    • From the folder \SysCADXXX\Setup\ReactionEditor
    • By downloading it from the SysCAD Downloads Page (, in the Utilities section. Once you have downloaded the zip file, you can unzip the installer for the Reaction Editor.
  3. Once the Reaction Editor installer file (.msi) has been obtained, run the installer and follow the steps outlined in the dialog boxes. If the default settings are used, the Reaction Editor will be installed in the folder C:\Program Files\SysCAD.
  4. The Reaction Editor uses the .NET framework (version 4.8).

Setting Reaction Editor as Default editor

GeneralOptions RxnEd.png

In SysCAD, select menu command Tools > General Options - General Tab page, under Editors (Reactions option)

  • if the reaction editor was installed using the default settings, then the path should have already been entered.
  • If not, press the SelectButton.png button and click the "Select Default: SysCADReactionEditor" option.

Once this is done, the next time you press the Edit Rct File button in SysCAD (see Opening Existing Reaction Files), the SysCAD Reaction Editor will start up.


  • You may still open the reaction files with a text editor, such as Notepad, Notepad++, etc., outside of SysCAD, if required.
  • You do not need to run SysCAD to use the Reaction Editor, so you can view and/or edit reaction files without loading a project (see Running Reaction Editor).

Location of Reaction Files

General - Reaction Folder Path.png When a new project is created, a sub-folder called Reactions is automatically added, any reactions created within the project will be automatically added to this folder. The picture shown here is for the Demo Nickel Copper Project.

This folder contains the file 'SpeciesData.ini', which contains all of the information about the species used within the project. The SysCAD Reaction Editor uses the information in this file to display the available species, determine if reactions are balanced, autobalance reactions if required, etc. The SysCAD Reaction Editor will automatically save any new reaction files into this folder.

For quick access to this folder from within the Reaction Editor, you can select File > Open Containing Folder or right-click a specific reaction file and select Open Containing Folder


  • If the user adds or deletes species from the SysCAD project while the reaction editor is opened, the user will need to:
    1. restart the SysCAD project to update the 'SpeciesData.ini' file
    2. restart the Reaction Editor to update the species list

Running Reaction Editor

If you followed the previous steps, then next time you have a project open, on any RB tab page, press the Edit Rct File button (See Opening Existing Reaction Files) and the SysCAD Reaction Editor will start up.

  • It will show all reaction files in the current project. The reaction file shown in the window will correspond to the one specified on the RB tab page chosen.

Alternatively, you can simply run the Reaction Editor without SysCAD. You can do this by either selecting SysCAD Reaction Editor from the list of programs in the Start menu, or going to the installed folder (usually C:\Program Files\SysCAD or C:\Program Files (x86)\SysCAD) and running the SysCADReactionEditor.exe file. When opening the Reaction Editor this way, no reaction files will be loaded.

  • To load a reaction file, use the File > Open command to browse for the desired reaction file (saved in the Reactions subfolder of a project).
  • To load all the reaction files for a project, use the File > Open Folder command to browse for the Reactions subfolder of the desired project.

Reaction Editor Options

ReactionEditorOptions.png On the main Reaction Editor Edit menu, there is an Options field.

This field has two options which can be enabled or disabled:

  1. Autoload All On Startup: If enabled, all reactions files in the current project will be loaded when the reaction editor is first launched
  2. Enforce Charge Balance: If enabled, Charge imbalances in reactions will be reported as errors.

Reaction Files

Creating a New Reaction File

A reaction file can be automatically created when you press the Edit Rct File button.

  • The RCT_Name field can be left empty, in this case, the reaction file name created will be "UnitName".rct, so for the example used in the picture above, it will be Ni_Diss_2.rct.
  • The RCT_Name can also be typed in prior to pressing the Edit Rct File button. If the file does not exist, it will be created for you.
  • The first time a reaction file is created in a project, the Reaction Editor will start with a blank reaction.
  • Please see Defining a New Reaction for information on how to add the reactants and products.

Opening Existing Reaction Files

Once SysCAD has been set to use Reaction Editor (see Setting Reaction Editor as Default editor), reaction files can be opened from SysCAD by pressing the Edit Rct File button.

Reactions - Edit rct.png

The SysCAD Reaction Editor will start up and shows all reaction files in the current project with the selected one being in the current window. See example below:

Reactions - Reaction Editor 1.png
Number Description
Button Small 1.png The existing reactions are displayed in the reaction Window.
Button Small 2.png The reaction editing panel will show details of the selected reaction, such as reactants, products, reaction extent, heat of reaction override and so on. Use this to edit the reaction.
Button Small 3.png The species used in the currently selected reaction are in bold and in blue in the species list in the right hand side window. The species used in other reactions in the current reaction file are in bold and in black in the species list in the right hand side window.
Button Small 4.png The filter can be used to shorten the display of the species list. For example, type in (aq) will show only the aqueous species, or type in Ni will display species containing Ni only.
Button Small 5.png The Title bar shows the current reaction file name.
Button Small 6.png All the reaction files in the current project are listed here.
Reaction list.png
  • Files in Grey colour are in the same project but have not been opened in the Reaction Editor, click on the file to open it.
  • Files in Black have been opened in the Reaction Editor and have no unsaved modifications.
  • Files in Blue have been opened in the Reaction Editor and have unsaved modifications.
Button Small 7.png This shows the species database location. See note in Location of Reaction Files
Button Small 8.png The log window will display any messages/warnings/errors found by the Reaction Editor. To clear the log go to View > Clear Log.

Saving and Closing Reaction Files


If a file has been changed it will be blue in the left hand side window and have an '*' next to the file name on the top of the reaction window. If there are any unsaved changes to the file, the user will be asked if they wish to save the file prior to it being closed.

Reaction files can be individually closed either by using the menu command File > Close or clicking on the X in the top right corner of the reaction window.

Editing the Reactions

Adding a New Reaction

The first time a reaction file is created in a project, the Reaction Editor will start with a blank reaction.

If additional reactions are required, press the Add Reaction button in the Reaction Display Window Button Small 1.png.

Defining a New Reaction

For example, let's add the following reaction, note it is in an unbalanced state:

[math]\ce{ FeSO4(aq) + O2(g) + H2SO4(aq) \; = \; Fe2[SO4]3(aq) + H2O(l) }[/math]

The image below shows a new reaction being added:

Reactions - Add Reaction.png
Number Description
This table continues from the previous table in Opening Existing Reaction Files, refers to the numbers listed in that table.
Button Small 9.png Reactant box - drag the species from the species list Button Small 3.png to here. Users do not have to type in the + signs when using drag and drop, simply drag and drop all the reactants. For our example: These are shown with a green dot in the above picture, we will also need drag in O2(g), which is not shown in the picture.
Button Small 10.png Product box - drag the species from the species list Button Small 3.png to here. Users do not have to type in the + signs when using drag and drop, simply drag and drop all the products. For our example: These are shown with a purple dot in the above picture.
Button Small 11.png Balancebutton.png button - Once all the reactants and products are placed in the boxes, press Balancebutton.png to balance the reaction. See Balancing the Reaction.
Button Small 12.png Reaction Extents - Specify the reaction extent type, values, and the extent species. Please see Reaction Extents for more detail.
NOTE: If a % is shown next to Value field, enter as percentage, otherwise, Value is a fraction.
Button Small 13.png Heat of Reaction - SysCAD normally uses the Heats of Formation of the products and reactants to calculate the Heat of Reaction. However, if a Heat of Formation value is missing in the species database for any compounds involved in the reaction, then user will need to tick the Override tick box and specify a user defined Heat of Reaction.
Button Small 14.png Once a reaction has been entered, its status will be shown just above the log window on the status line.

Note: Users should FIRST drag species into the Reactant and Product boxes and THEN adjust the number of moles of each species reacting, or use the automatic balance functionality.

Balancing the Reaction

Normally two things will happen when the Balancebutton.png button is pressed, user will either be shown the balanced reaction or be asked to specify extra species. We will explain these using two examples:

Example 1 Sufficient Species

For example, in the above topic, we have added the Ferrous to Ferric reaction,

  1. [math]\ce{ FeSO4(aq) + O2(g) + H2SO4(aq) \; = \; Fe2[SO4]3(aq) + H2O(l) }[/math]
    • This reaction is not balanced, users will find a message displayed in the Status bar: Status: Imbalanced. Excess product elements: {Fe = 1}, {S = 1}, {O = 3}.Button Small 14.png
  2. To balance the reaction, either
    • manually enter the number of moles of each species in the reaction;
    • Or press the Balancebutton.png button for suggestion from SysCAD.
  3. When the Balancebutton.png button is pressed, the Reaction Editor will attempt to balance the active reaction with the specified Reactants and Products.
    • The Autobalancer will display both the original and some options for a balanced reaction:
    Reaction Editor Balancer with Options.png
    • The user may then either:
      • Select one of the balanced options (Fraction, Decimal or Whole Number) and accept the changes by pressing 'OK', or
      • Reject the changes by pressing 'Cancel'

Example 2 Insufficient Species

For example,

  1. If a user simply enters Ferrous and Ferric as reactant and product, and nothing else, then pressed the Balancebutton.png button,
    ReactionEditor Insuf Sp.png
  2. As we are missing sulfuric acid, water and oxygen, we will have the "Autobalancer Additional Species" dialog box opened:
    Reaction Editor Balancer 2.png
  3. When this happens, the user can either:
    • click on 'Cancel' to return to the Reaction Editor, add additional species to the Reactants or Products and try Balancebutton.png again; OR
    • use a previously specified group of species, or set up a new group of species for balancing reactions.
  4. In the dialog box above there are no previously specified species groups that are useful for this reaction, and hence we will define a new Species Group
    • Type in a name in the Species Group box
    • Type in the name of the required additional species, including phase, with commas between species.
    • You CANNOT drag species into this dialog box, but can select from a drop list after the first letter is entered as shown below:
    ReactionEditor Species set.png
    • After all the additional species are entered, you can press OK and the reaction can now be balanced:
    Reaction Editor Balancer with Options2.png
    • The user may then either:
      • Select one of the balanced options (Fraction, Decimal or Whole Number) and accept the changes by pressing 'OK', or
      • Reject the changes by pressing 'Cancel'


  • When a species group is saved, users can use it again to define other reactions.
  • The species groups can be managed via the Reaction Editor menu command Edit > Auto Complete Sets..
    ReactionEditor Species set1.png ReactionEditor Species set2.png
    • If a species group is no longer required, press the Delete button to remove it.
    • For a new group, simply change the name in the species group and modify the species in the group as we have done in Example 2 above.
  • This functionality is especially useful when the user has a number of reactions that involve the same reagent and by-product.
    For example, using the SulfuricAcid species group (with additional species H2SO4(aq) and H2O(l)), we can simply drag in the main reactant and product, and the autobalancer will fill in the additional species from the species group:
    ReactionEditor Species set5.png
  • Please see Video Link for a video showing you how to set up and use a Species Group in the Reaction Editor.

Adding a New Source

Reaction Source.png
Number Description
This table continues from the previous tables in Opening Existing Reaction Files and Defining a New Reaction, refers to the numbers listed in previous tables.
Button Small 15.png Press the Add Other Button, select the Source radio button.
Button Small 16.png
  • The source species can be added in a number of ways:
    1. Drag the species from species list Button Small 3.png and drop into the Source Species box
    2. Right click on the species in species list Button Small 3.png and select set as Source
    3. Manually typed in.
  • Any species being used a source will have a Source icon.png icon displayed next to it.
  • You may only add a Source once to a reaction file, but you can add multiple species to a single Source.
  • The source will always be reaction 1.
Button Small 16.png Select what the source should be treated as: Source only, Recycle only or Source and recycle. Please see Reaction Source for more information.

Adding a New Sink

This is similar to Adding a New Source. The differences are listed here:

  • Click on Add Other and select Sink.
  • Any species being used as a sink will have a Sink icon.png icon displayed next to it.
  • You may only add a Sink once to a reaction file, but you can add multiple species to a single Sink.
  • The Sink will always be the last reaction.
  • Please see Reaction Sink for more information.

Adding Heat Exchange

  • To add Heat Exchange, click on Add Other and select Heat Exchange.
  • In the Heat Exchange box, select the appropriate option from the drop down list and then specify the value of associated variables depending on options chosen.
  • These options are explained in Reaction Heat Exchange.

Removing a Reaction, Source, Sink or Heat Exchange

  • To remove a reaction, source, sink or heat exchange, simply select it in the reaction window and click Remove.
  • If you only wish to disable the reaction, source, sink or heat exchange, clear the Enabled box at the bottom of the reaction window.

Specifying the Reaction Order

By default, SysCAD reactions are added sequentially. Alternatively, user can choose to specify two or more simultaneous reactions. Simultaneous reactions requires the Sequences Enabled option to be on.

  • The reaction order is as they appear in the reaction file. To change the order of the reactions in the reaction file, select the desired reaction in the reaction window and click the up and down arrow buttons to move to the desired place in the reaction file.
Reaction order.png


  • If included, sources will always be first, sinks will always be last or second last and heat exchange will always be last (as shown above). These cannot be re-ordered.
  • The reaction file in the picture shown above started with an existing reaction file, then new reactions, sink and HX options were added for demonstration purposes.
  • Any reaction with "*" marked means it is new or has been modified, and the new information has not been saved yet
  • If the reaction has been saved previously, and the order is now changed, then a number in (x) will shows the reaction order change. In the example above, the reaction 5 was saved as reaction 2 before the move.
  • When the reaction file is saved, these markers will disappear.

Other Features

Right click on a reaction in the Reaction display panel will bring up the following pop-up options:

Reaction rightclick options.png

Most of the features have already been explained in previous headings. The remaining are explained below.

Clone a Reaction

The user may wish to clone a reaction when a very similar reaction is required. Select the required reaction in the reaction window and click Clone. A new reaction will be created at the bottom of the list which can be edited as for other reactions.

NOTE: when editing a cloned reaction, be sure to check and edit the extent species as this may have changed, especially if the "old" compound has been deleted.

Reversing a Reaction

A reaction may be reversed (swap Reactants and Products) by right-clicking the reaction and selecting Reverse Reaction. You may need to then update the extent settings depending on the extent type.

Copying Reactions from other opened files

Reactions can be easily copied from one reaction file to another using the Reaction Editor.

If the reaction files are in the same project, and they are both opened in the reaction editor, then

  • With the Files pane open, drag the reaction to be copied with the left mouse, hold down and drop it into the other reaction file.
Reaction editor 3.png

Copying from another instance of Reactions Editor

To copy a reaction from a reaction file in a different project, open the reaction files in a different instances of the Reaction Editor.

Button Small 1.png Select the reaction to be copied, <ctrl+C> or right mouse click and select copy.
Button Small 2.pngGo to the other instance of Reaction Editor, right click on the reaction window of the desired reaction file and select paste.


  • Existing Reaction Files can be opened from the SysCAD Reaction Editor without starting the SysCAD project.
  • Start up the Reaction Editor from the start menu. Menu command <File> - <Open> and select the reaction file to open.
  • Alternatively, with one instance of the reaction editor opened, Menu command <File> - <Open Folder> and select the reactions folder for a particular project. The files will be opened in another instance of the Reaction Editor.

Options Tab

For every reaction file there is a Options tab. Click on the tab to access the Options tab. An example is shown below.

Reaction Editor Options.png

This tab allows the user to enable the following:

Sequences Enabled

  • This causes the reactions to be solved simultaneously, if required. This is NOT the recommended solution method - please see Reaction Block - Solving Reactions for more information.
  • With the Sequences Enabled option ticked, each reaction will automatically be assigned a Sequence number of 1 - which means that all of the reactions are placed in sequence 1 and solved simultaneously.
  • The user may change the sequence number of a reaction on the Reactions tab Button Small 1.png and hence create groups of reactions. Each group of reactions is solved simultaneously. In the example shown below, we have moved one of the reaction to a second sequence for demonstration purposes.
  • Note that this does not affect Sources, Sinks and Heat Exchange. Source species will be added before the first sequence. Sink species will be removed and Heat Exchange will be performed after all sequences are solved.

Always Use First Reactant for Extent

  • This allows the user to specify that the first reactant is always to be used for the extent for the reactions in this reaction file.
  • Normally when a reaction is inserted the default extent species used is the first reactant, but the user may change this. If this option is enabled, then the user cannot change the extent species.


  • Add any comments to the description box for this reaction file.
  • Any comments which were previously in a reaction file created without the Reaction Editor will be automatically moved to the description box. The date that the file was first saved using the Reaction Editor will automatically be noted in the description box as shown in the example above.


  • If you are getting this error message during the reaction editor start up: "An item with the same key has already been added", it may be caused by issues with the species database definition. Please check the message window - species database tab for any errors. Please see general notes for more information.