Q. What is the latest version of the CRW? Where can I get it?

A. The latest version is 2.0.2 and it was released on March 20, 2009. You can get this version from the CRW download page.

Q. What changes have been made to the CRW over the years?

A. On the CRW Development History page, you can learn about the changes made to each version of the worksheet.

Q. Who created the CRW?

A. The CRW was developed by NOAA's Office of Response and Restoration in collaboration with the Environmental Protection Agency and the Center for Chemical Process Safety.

Q: What is chemical reactivity?

A. Chemical reactivity is the tendency of substances to undergo chemical change. Some chemical changes are harmless, but others can lead to hazardous conditions. For example, two chemicals might react together and produce a toxic gas or cause an explosion. You can use the CRW to add chemicals to a virtual mixture, and then predict the hazards that could occur if chemicals in that collection were to mix together. You can also access datasheets on individual chemicals to view information such as chemical profiles and special hazard alerts.

Q. What are reactive groups?

A. Reactive groups are categories of chemicals (such as "acid halides" or "ketones") that react in similar ways because they are similar in their chemical structure. For the purposes of predicting potential reactivity between chemicals, each chemical in the CRW has been assigned to one or more reactive groups, based on the known chemistry of that chemical. (To see descriptions of all the reactive groups used in the CRW, click "Add Reactive Group" from the main worksheet page in the program.)

Q: How does the CRW predict reactivity between chemicals?

A. To predict the potential reactivity of a mixture of chemicals, the CRW first identifies the reactive groups to which the chemicals belong, and then predicts the kind of pair-wise reactions likely to occur when members of these groups are mixed together.

Q: What are pair-wise reactivity predictions?

A. The CRW only accounts for reactions between two chemicals at a time. If you have more than two chemicals on your reactivity mixture worksheet, it predicts the reactivity between all possible pairs of those chemicals.

Important Note: When there are three or more substances in the mix, they may react together in ways that the CRW's pair-wise reactions can't predict:

• For example, glycerin and nitric acid react very little when they're mixed together. However, if sulfuric acid is added to the mix, the three chemicals react together to produce the powerful explosive nitroglycerin. The CRW doesn't predict this reaction, because it looks at the pairs (glycerin + nitric acid; glycerin + sulfuric acid; and nitric acid + sulfuric acid) rather than all three chemicals together.
• In other cases, one of the chemicals may act as a catalyst that accelerates the rate of reaction between other chemicals in the mixture. For example, nickel carbonyl catalyzes many polymerization reactions and other kinds of synthetic organic reactions. In such cases, the reactivity hazard may be greater than predicted.

However, reactions among more than two chemicals are relatively uncommon in nature, except for the catalyzed reactions that are common components of the metabolic processes of living organisms.

Q. Can I add as many chemicals as I want to a mixture?

A. The current limit is 50 chemicals.

Q. Is there a way I can add additional chemicals to the CRW's database?

A. Yes. Beginning with version 2.0, you can add your own chemicals to the CRW database. Once they're part of the database, you can add them to the reactivity worksheet to see how they might react with other chemicals in the database. On the main worksheet page, click the "Add Custom Chemicals" button to create and manage your custom chemical list.

Q. Is there a way to see how chemicals in the mixture react with water?

A. On the main worksheet page, click "Add Water" to include water in the mixture. (This will allow you to see general predictions about how the chemicals would react with water. However, if a chemical is water reactive, there may be more specific information on its chemical datasheet.)

Q: Can I add a reactive group to the mixture?

A. You can add reactive groups—as well as specific chemicals—to a mixture. You may want to do this if, for example, you know that a substance is a base, but you don't know its name or CAS registry number. On the main worksheet page, click "Add Reactive Group", select the name of the group that you want to add, and then click "Add Selected Group to Worksheet".

Q. I used the CRW to "mix" some chemicals together, and it predicted "No reaction expected." Should I trust this prediction?

A. We believe that the CRW accurately predicts whether or not a reaction will occur between two chemicals that you select. But sometimes, there's more to the story. For instance, to predict the reactivity of a mixture of more than two chemicals, the CRW predicts the reactivity between all possible pairs of those chemicals. But sometimes, three or more chemicals can react together in ways the CRW can't predict. In some cases, for example, a chemical may catalyze (speed up) the reaction between two other chemicals, making that reaction more violent than the CRW would predict.

There are multiple places in the CRW where the program alerts you to hazards, and you should review all of them when assessing reactivity:

• Chemical Datasheet: Once you've added chemicals to the mixture collection on the reactivity worksheet, double-click on the name of a chemical to go to its chemical datasheet. The datasheet provides a general description of the chemical, a list of special hazards, a chemical profile (focused on reactivity), reactive group assignments, and details about whether the chemical reacts with air or water.
• Mixture Worksheet: Once your mixture collection is complete, click "Predict Hazards" on the main worksheet page to display the potential hazards at the bottom of the page. After you have studied the predicted hazards, click the "Mixture Documentation" tab to see research related to this combination of chemicals. Keep in mind that the results of this research (or the described events) may not match the results of your mixture—possibly because the chemicals or the scenario conditions are slightly different.
• Compatibility Table: After you've reviewed the predictions on the worksheet, click "Show Compatibility Chart" on the main worksheet page. On the table that appears, you can click in individual table cells to see the reactivity details for that pair of chemicals. When you've selected a cell, the predictions for specific hazards and potential gas products are listed on the bottom of the page, along with documentation about the reasons for those predictions.

Q. When I combined nitric acid and sodium hydrosulfide, one of the hazard statements was "combination liberates gaseous products, including both flammable and toxic gases." Can the CRW tell me what flammable gases could be expected?

A. Yes. Open the Compatibility Chart, and click on the cell for that pair of chemicals. On the "Potential Gases" tab at the bottom of the page, the CRW shows you that it predicts that sodium hydrosulfide mixed with nitric acid produces hydrogen sulfide and acid fumes.

Q. Do you have CRW for Windows 7 64-bit operating systems?

A. The CRW is compatible with Windows 7 64-bit operating systems. If installed and run on a 64-bit operating system, it will run in a 32-bit compatibility mode.

Q. Do we need to obtain either individual or site licenses to use the CRW?

A. No. The CRW is free, as are all the programs in the CAMEO software suite.

Q. Can we run the CRW from a server?

A. Yes. Beginning with version 2.0, the CRW may be run off of a server.

Q. What kind of software is the CRW?

A. Beginning with version 2.0, the CRW was created with FileMaker Pro, a 32-bit, cross-platform, fully relational database program that allows us to "bundle" the chemical data with the FileMaker Runtime engine.

 
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